Because kids don't have a choice. Kek
Maybe they take length of the cachpa and just flood it with random alphabet sequences.
If it would be possible I would try to make random length of catchpa like from 6 - 9 symbols, that way bot would be forced to generate sequence from 6 to 9 which would require much more resources.. I guess :D
I doubt bot reads pic's, maybe they can scan it, but still they would try like this guy say
>brute force it.
send request -scan/randomize -> send request -> scan/randomize (repeat while you break it)
And still I think with fix'ed length it is more possible to break it.