To answer the OP, the $25 is a little low. Our per diem is higher, but there's a $25 cap on any one meal. I think that's reasonable for a single traveler.
As a PP mentioned it is meant to offset costs not completely cover all.
When I traveled often, that was the company policy. The per diem varied based on where you were traveling to - big cities were typically more expensive for food than other places. The hotel usually includes breakfast, salad or sandwich/soup for lunch ($6-8) and dinner would vary. Since I was working, I often ordered in, which would be around $6-10, or I'd go out to a diner or restaurant for $20. On average, I would spend around $35/day. I usually travel alone, though, so it's not like I'm hanging out in the restaurant. I'm perfectly happy picking up a chicken pot pie and bringing it back to the hotel to eat while I catch up on my personal life.
If you were at home, you'd be spending an unreimbusable amount per day. This is on top of that amount. The per diem isn't your spending limit, it reflects how much of the bill you could expense. You want a $50 steak, no one's stopping you, but the company would only foot the bill for $25 of it, lol.
Just to throw fuel on the fire, one company that I worked for had a "no alcoholic beverages" policy. If you bought it, it was your money paying for it - you couldn't expense it unless you had a client or vendor with you. Then, you could expense the whole bill as "entertainment."
The US Per Diem Rates are listed here :
www.gsa.gov/portal/category/21287
Honestly, I love traveling by myself. I don't have to cook or serve meals, worry about what others want to eat, I can watch whatever I want on TV, go visit friends or work out whenever I like. I think of solo traveling as a retreat from my everyday life. I know how tight money is for my employer, so I don't abuse the system.
Off-topic:
??? Being reimbursed for missing kids' activities ??? That's not the intent of a per diem at all, as any regular business traveler will tell you. Most people who travel regularly are well-paid for it in their compensation. If you don't want to travel, don't take the job. To be resentful and expect to be compensated is a recipe for unhappiness.