And since that became the standard from the beginning, it's what remains now.
1st Tier schools a Bachelor's degree holder has most of the fundamentals of mathematics within computer science. Complexity of algorithms, complexity of operations on various data structures, models of computation, problems that can be solved with different models, etc..
20 years on from going to school it took me a long time to figure out a lot of schools don't cover almost all of that until you're working on a Master's degree or Ph. D. It's really surprising.
I think some of CS questions in interviews are because the degrees are so variable. I don't think this is a problem when you're hiring a Mechanical Engineer or a Civil Engineer who is licensed. All the schools need to teach to a uniform enough standard that their graduates can pass the licensing requirements.
CS is a mess. The Top Tier schools seem like they may be so much better that a Bachelor's degree is worth more than a Master's degree from other places.
I think it's hovering around medicine. Where there is a seemingly art form to deal with the realities of our too complex biology.
I've long suspected that much of what the algorithm testing craze (and other grilling on "strong CS fundamentals") in the current default hiring process boils down to is -- they just want to have some kind of vague reassurance that the people they're hiring are somehow "better" than the folks the other companies are hiring.
Even if the standards of "better" (and they means of measuring it) are - when we think about it - pretty dubious.
(To head off some of the tangential discussion that would otherwise likely ensue from what I just said: I don't dispute the value of doing some algorithm testing -- the point is that a lot of places seem to overtest these days, and it seems also that the only reason they're doing it is because they think that's what other companies - or at least the ones they'd like to fantasize that they're emulating - are doing).