Renting a domain for the the sole sake of selling the ability to rent it to someone else or even worse: Renting it at a higher price to someone else and pocketing that extra money every year without providing any additional service. Bonus points if you also track recent companies that have been created and immediately buy also the related domains and social media handles and extort the founders of the new companies.

With real-property squatting is using what someone else owns (land) w/o permission. Domains are only rented. If you rent land but don't use it the way someone else would it's not squatting. So, renting a domain that someone else wants and not using it in the way they think it should be used isn't squatting, correct?

I agree it's a problem when I want a domain and it looks unused to me. I don't think it's really squatting.

I think it's also a jerk move to control resources just to extract w/o developing those resources. But that also happens with real-property.

All that to say: "squatting" on a domain is a "hard problem".