[ronaldx]

Yep: a better reason (than those given on SO) is that it's designed for minimal UX annoyance - it is least likely to cover up what you need to see while still serving its purpose; the asymmetry allows you to more quickly understand which point is important.

It's instructive to observe the circumstances when the cursor changes: there is some indication of context change, but also the design of the cursor in each context is important.

[tlunter]

A better reason in hindsight isn't the right answer. Likely they had to do it per limitations of the computers of the time. Trying to tie it to UX like a modern day designer is just wrong.

[rch]

It's probably not a good idea to underestimate the depth of the deliberations that actually took place at the time, based on a necessarily pragmatic justification for the accepted decision.

[ronaldx]

Absolutely disagree.

As discussed in the accepted answer, vertical line cursors predate the slanted shape. Changing to a different style only makes sense as a design decision.