Most probably because of a reason mentioned here: https://www.davx5.com/faq/synchronization-is-not-run-as-expected
There’s not one URL, but a bunch of them, so you had to change all, and there’s risk of data loss and more problems. Also, there are cases whre you shouldn’t just change the URL (for instance, when you move to another server, which might calculate ETags another way). So, I recommend just to delete the account of the server which doesn’t exist anymore and add another account with the new URL. Should take about 1 min (for me, 5 sec, but I’m used to testing).
If you find a useful algorithm for changing “the URL” which is maintainable, not dangerous, user-friendly and covers all use cases, please let me know or, even better, send a merge request Thanks!