>>13430189
A slow cut allows the cheese to harden back up again. So while it appears you're about to get a big juicy wad of melted cheese, a third of it has already hardened back onto the block and another quarter will too by the time they've finished cutting.
I went to one of these 'pop up' bullshit raclette stalls at a fair, and he barely used any cheese all night. Kept heating it up, then making a big show of scraping it off, and in the end the customers got very little.
As with most things, greed is the issue.