YSK: most (if not all) "toy crane" machines are programmed to only lock the claw into place every x attempts

For a machine with small "junk" toys or stuffed animals, it might be set to lock the claw on an item every 5 or 10 attempts or a low number like that. "Big prize" machines that have expensive electronics or other impressive prizes might be ridiculously high, like every 100-1000 attempts or more. There is really very little skill or luck involved beyond moving the claw or grabber into place.

Source: I worked in an arcade for a while.