I am sure there are good reasons to rewrite software but I have seen so many projects attempt some major rewrite that ultimately fail to deliver on the promised value, take a lot longer than expected, and end up with a whole bunch of new problems that the old system didn't have.

[1]https://news.ycombinator.com/item?id=36642796#36646055

[2] https://www.joelonsoftware.com/2000/04/06/things-you-should-never-do-part-i/