It's just a case of tall poppy syndrome.
I really can't be bothered posting here much anymore... I feel like we are all parrots going over the same arguments time and time again.
Vettel has always given his team due credit. Always says the car was perfect after every race win. Any moment he says anything that can be slightly construed as otherwise, gets pounced on and used as more ammunition against him.
But even people who hardly watch F1 turn on the tv, see Vettel give an interview and say he's arrogant. The thing is, similar things were said of Hamilton and Button when they were winning. Rosberg tried it on after his first couple of wins, but is now probably the most pleasant driver on the grid - I love his post race interviews.

My Korean flatmate who hardly ever watches F1 came in the other day, pointed at the screen at Vettel, and said in his broken English: "This driver.... always winning."
The driver driving the best car will always win the title 9 times out of 10. The last driver to win a championship without the best car was Raikkonen in 2007. Then probably Keke Rosberg in 1982? The years between them it was always either Mclaren, Williams, Ferrari and Renault dominating the seasons.
So the very nature of F1 - the sport we profess to love - is superior racing machines with superior athletes driving around in circles and trying to be better than everyone else at it. It was always about trying to innovate new technologies to be faster than everyone. But you can't do that with a drop-kick driving the car; he has to be fast and consistent so that the team can improve the technology over the course of the season.
If you can't get used to the fastest car always winning - go and watch Indycar or Nascar or something... Or, maybe the sport will finally bow to pressure from racegoers and just become a spec-series. Even my aforementioned Korean flatmate doesn't think it's fair on the drivers that the cars are different.
But the moment they switch to a spec series will probably be the time I stop watching Formula One.
It really is frustrating trying to talk to fans of this sport. I only really started thinking about F1 when I got my first Playstation in 2005 and played the game based on the '95 season. Ever since then this small spark has kindled into a burning passion. The thing is, the arguments that F1 fans have are never the same as fans of other sports. Football fans and Rugby Fans never have to argue or defend the reason why the team they support is so great. We just accept it. The only arguments seem to arise from refereeing controversies.
In cricket it's often arguments about which players should be picked for the national team, but we accept that the issue is that the Australian selectors are off their faces picking rubbish players, and that it's our team's fault for not being up to speed with the rest of the world. We don't keep waiting and hoping that the rules will one day change to level the playing field.
It's stupid though that that's exactly what F1 fans do. They kick up a stink about how the best team always wins, and then hope for a rule change to level the playing field. I have never come across a sport like this...
The drivers in the team are just like individual football players. Football teams make decisions to purchase the best players they can afford to make their team succeed. Sebastian Vettel is similar to Christiano Ronaldo. The teams pay big bucks to keep these guys on their team and do not want to release them to their bitter rivals to gain an advantage.
Sure Hamilton and Alonso are great, but Red Bull are the best team in Formula One at the moment and Sebastian Vettel is doing the job for them. The minute Vettel or Newey stop doing their jobs, they will be fired and then Red Bull will sign the next best replacement available to them.
Ferrari have tried supporting Alonso to get a WDC by keeping a sub-par driver in Felipe Massa to "support" him. But as Alonso on his own is unable to overcome Red Bull and Vettel in the Driver's championship and stand no chance in Constructor's, they are now changing their tact by going for 2 world champions in a bid to secure the WCC.
Regardless of anything that we speculate or say or do - you and I will never affect the outcome of a race or future championships. So either you can resort to jumping up and down complaining and wishing F1 would change, which is bad for your health - elevated blood pressure etc; or you could just accept that F1 is what it is.
Maybe too much focus is placed on the drivers. But it is just the same as any team sport. Who is the best football player in the world? Ronaldo or Messi? Why do clubs pay millions of dollars for them? A defender will never be regarded as the best player in the world - but they are a necessary part of football, just like designers and mechanics are in F1.
As for me, I will continue to watch Formula One and accept it for what it is. I'll continue to be awed and impressed by skills of the drivers that grace this wonderful sport. And I will continue to praise the teams (drivers + mechanics + engineers + designers) that dominate our beloved sport - and I just hope that this formula of dominant teams and drivers never changes....