I think that's a rather harsh assumption!

Also (as an aside), in some countries it is required to give up one's seat. In France, for example, there's a hierarchy of people who are entitled to the accessible seats on public transport. You can contrast that with the British approach, where the signs say things like, "Please consider giving up your seat for someone who needs it more than you do", or the US, where I imagine it's left to people's commonsense completely.

But I don't think it's safe to assume that the person who doesn't leave a big tip in an expensive restaurant will also not "give up his seat for someone that needs it more than he does".