The answers to "why" are many and varied, but possibly the worst answer possible is: "Because so-and-so said so."
That's not a reason, that's an excuse. Presumably, whoever said so had a reason for saying so, and that's the actual why. There are two reasons we get into this situation:
- Because that person is almost always right (or in a position of authority that effectively makes them correct)
- Because that person is a convenient target for blame
It doesn't have to be this way. "Because so-and-so said so" is a learning opportunity. It's a chance to understand better, both this specific scenario and how so-and-so got to be such an expert. Think of it as a chance to check your work.
"Why is there a limit of 255 virtual machines on this box?"
"Because John said so."
Well, John's a really smart guy, and he knows the product really really well, so presumably he has a reason for saying so. So why did he say so? "Because we use a /24 network, which allows 256 hosts, and we reserve one address for the physical box." See? Now you actually know something more about the product than you did before. You also know that there's potentially a problem there (networks typically allow 254 hosts, with .0 and .255 generally reserved).
Find out why someone said so.... it's illuminating.