Well many reasons:
more affordable travel and discover new places,
climate tolerance issues eg stay on summer on colder place and on winter on warmer place north-south axis exchanges,
get or find appropriate company if staying alone,
and many more..
Now its possible to request exhanges, but due ongoing corona issues, consider only near by,
for more distant locations check first if safe or possible to travetl that desitination, before making request or commiting exchange.