acount6672
The TAs hold discussion sections (also online), hold office hours and grade exams. I don't think it is unreasonable to limit the number of students per TA.
There are similar restrictions on my time (I can only have so many students before it becomes impossible to answer questions in lecture or office hours). But I think these considerations are less restrictive.
Moreover, even if one doesn't care about how much work the TAs and I might have to do, it is very difficult bureaucratically to increase the number of students per TA. There are department policies limiting this number, university-wide policies, and union contracts.
Oh, and there are looming budget cuts, which will probably reduce the number of TAs available and lower maximum enrollments.
I only wish the AMD desktop and workstation machines could support more RAM. I have 256GB on the Intel machine, whereas 128GB was the max for the 3900x. I think the threadripper line only goes up to 256GB, which seems a little low for machines which such a large core count.