Why rewrite if thing exists?
You can use those expensive engineers to build more stuff, not rewrite old stuff
Cause it's (allegedly) cheap and you can do much better? Avoiding rewriting things should become a thing of the past if these tools work as advertised.
Why not rewrite if code is free
Why create Windows when MacOS exists?
Why create Linux when UNIX exists?
Why create Firefox when Internet Explorer exists?
Why Create a Pontiac when Ford exists?
Why do anything you think can be done better when someone else has done it worse?
For some people the relevant properties of "thing" include not needing overpowered hardware to run it comfortably. So "thing" does not just "exist", at least not in the form of electron.