Paying for the service is paying for the service; bundling it with support costs would just make it cost more for people that don't need support.

Google specifically seems to target their services much more at the large enterprise, rather than small companies and individuals. Enterprise will always pay for support, so if they are your target market, it's a given you can get them to pay. It's less of a necessity for providing lower costs, and more of a business decision to not expend resources to acquire customers that aren't bringing in tens or hundreds of thousands of dollars every month.

$10-20/month VPS providers often respond to, and actually take action, on tickets within 5-15 minutes at no extra cost. Of course there is no guarantee, and a ticket can certainly wind up unresolved for 24+ hours. In my experience, if the ticket you file clearly explains your issue and represents something they can realistically help you with, the level of service provided for such a low server cost can be exceptional.

For a comparision, AWS also makes you pay for prompt support, and all of their services cost money (unlike AppEngine which has a lot of free services).

> all of their services cost money

I'm not sure what you mean by this. Every AWS service I can think of has "free tier" for lower use and then charges for higher use, like AppEngine. For example, AWS's email service (SES) is free up to 60,000 emails per month.