This argument does not take bandwidth into account. If the goal is to download a lot of different files, you will be effectively limiting your download with keeping (especially very popular) torrents seeded. I stand corrected if somebody could please disprove me.

As the other commenter said, upload and download speeds are separate. And if you mean data caps, most internet connections have "unlimited" bandwidth unless you're torrenting off your phone.

Isn't bandwidth up- and download independent usually, so seeding (uploading) would not affect your downloads?