During the teenager years, (if) the business is still profitable and hasn't bankrupt itself the business owner start noticing the need for formal operation procedure manuals. They've either felt the pain of the lose of key developer and or customer and they to secure their position within the market place. Typically this is where in one form or another organisation charts come into existence and more formal documentation and processes start. Either in this time/frame you have HR/Sales/Support starting to take form.
During the maturity years, most of the teenager years of formalizing and documentation of procedures manual is in full swing. You have well defined organisation charts with formal processes to follow and legal department to sign off on new contracts. You have the existence of Managers of each department to coordinate the necessary sales goals, and marketing goal for the business.
In each of the three different phase you have cultural shifts. From young and dream focused. Then the shift during teenage years of reigning in the younger attitudes and formal processes. Then finally to the maturing phase where for better or worse a more mechanical and empirical processes of doing business.
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.
This is why I decided to start my own company again after 4 1/2 years at Square.
This way age becomes an asset rather than a liability.