Because it's more affordable (at least in the long run), plus all those games have been ported... also we have "free" games now, 30 years ago was the "beginning" of video gaming, not the big industry it's now. Throw internet into the mix...
I guess what I'm trying to say is things have changed a LOT. 

 @kamehamic Yeah, but why haven't those things filtered back into arcades? Why do they still have games with PS1 quality graphics? 

 I'm not up to speed on what's in the arcades now, are the games recent? for reference the most recent stuff I remember in arcades are the DDR machines. 

 @kamehamic Yep. And that was still there. an OG DDR.