When I look at my servers I see lots of scanning on port 22. Most of them are not via Tor exits, but using other machines. So I think it doesn't make much difference if Tor would disable that by default.
In the case of port 22 it is in the hands of the administrator to take care of appropriate means. If the port scanning bothers you one good idea is to ...
As onion services "live" within the network, you don't need to be an exit to relay onion service traffic.
See https://2019.www.torproject.org/docs/onion-services for details.
Exits are "only" needed for exiting to the clearnet.
Thank you for running any relay.