I think it’s just because most players tend to be good at micro, but not so much macro.
Having a set “build” takes the macro thought of your item choice out of the equation so they can focus on their micro. The thing is though, you can easily make up for subpar micro with good macro. Picking the best items for a given situation, even if they aren’t necessarily “meta” is incredibly important and something most players just don’t feel like mastering.
Hopefully not soon, but probably once Gabe is gone if i had to guess.
If steam goes public, might as well start packing the bug out bag because shit is going to go south real quick.