When I worked as a computer consultant for a large consulting company years ago, I ended up working onsite in a number of different states, and having to do state tax returns in some of them. But that was because the work I was carrying out actually took place in those states.
With remote access/work from home, onsite work in the IT world is much reduced.
I am currently logged in to a server that is somewhere in Asia.
Not sure that state tax laws have caught up with these situations.
My current employer is based in one state, I live in another, our US based facilities are in multiple states and our IT infrastructure is in multiple countries.
The company I work for we have to enter the location where we performed the work. Even working from home.
I have worked several times (in the past) in California, but every time for less than 30 days. I think I’ll tell my bosses that I will never work there again for more 30 days in any future year.