It sounds like the catch is that you grant them "a royalty-free, transferable, perpetual, irrevocable, non-exclusive, worldwide license to use, reproduce, modify, publish, list information regarding, edit, translate, distribute, syndicate, publicly perform, publicly display, and make derivative works of all such User Content"[0].

Perhaps this is the start of a massive stock photo/video company?

[0] https://www.streem.com/terms

Edit: Or even if it's not the start of such a company, it would look awfully tempting for a company in that space to acquire. Having thousands of terabytes of media data, and the rights to modify and distribute it, can be very valuable.