Jurassic World Evolution - Mcrosoft Store versus Steam

Yes, because all these programs have coding inbedded in them by the distributors like how all the steam games work with steamoverlay and vice versa with xbox. Unless you find the appropriate file to copy all the DLC folders into, even still i highly doubt
youd be able to get it to run.

because some of the microsoft versions on pc are locked down port overs from the xbox and they reside in an encrypted folder. and they are from different stores and like most stores you cannot mix and match dlc.

But why, both work on PC?

Should I now buy another copy of the main game from Microsoft store and install it also on my pc? It doest make any sense

I don't think you will as steam and Microsoft operate differently

It´s not the same story, every video game company has his own licenses.