Is vendor support a myth?

In my last (n) years of software development experience I have never come across a scenario when the team had rued for implementing a solution with open source products. Infact on a few occasions the decision of choosing a vendor was regretted. BTW, I am not alone. I asked the same question with people with varying role and got pretty much the same reply - Not yet. So, why do the companies purchase products from an external vendor when a competing opensource products are readily available? The answer is simple - for the myth of getting the vendor support. It is cheaper in the long run, we do not have to train our IT, Its like an insurance policy - you pay even if you don't need it, etc etc etc. I am confused because I believe by hiring few good programmers and deploying a similar opensource product works as beautifully as the pricey vendor app if not better. After all, its rare to not have any IT division (insourced or outsourced) then why not make a good use of them?