There is an extent to which culture fit is an appropriate discriminator, but writing people off based on their age is taking it too far.
Do I think I will fit into a young crowed who have absolutely no social circles outside of work in their 20's now? The answer is no. Do I get approached by startup's to start some new fancy facebook clone every 2-3 weeks? The answer is 'yes' but I decline their offer's.
Care to provide examples? Also I've never heard of engineers being interviewed on ethic principles.
I'm fairly sure those criteria are all illegal, at least in most U.S. states if not at the federal level.
Also, it's a huge leap to say that discrimination is motivated by profits. I have no idea how you worked that one out.