I went out to eat a VERY cheap diner in Flint, MI. Basically about the cheapest place possible one should be able to eat. For an omelet, Small order of fish and chips, and fried cauliflower, no drinks, the bill was nearly $35. A few years ago each of those items would have problem been $7, so a $20~ish bill total.
Not tip-related, but just showing how it's getting less and less feasible to eat-out on ANY sort of budget...
Now...I'm always a 20% tipper because that's how I was raised. I'd just stop going out to eat rather than tip less. But this server used to work with my wife years ago, so now there's the extra social pressure to tip EVEN MORE because it's someone you know, and even more