i think the games volatility goes up as the stake goes up. gorilla megaways for example can pay 5000x on 10p (50p) spins, (iv had it myself) but can you imagine hitting that on say a £4 spin? which would be £20 a spin. its not going to give that out very easily, same goes for most games.
I do belive however that the slots are not "random" as they state to be. a megaways for example again, can be a complete hit and miss in the base game depending time/day it is. 1 minute it can be playing really well, then it can rip 100,200...500 in a matter of minutes and suck you dry. the MW bonuses are terrible, 1 or 2 spins of a hit, if your lucky enough the game gives a half decent x win. then eill just dead spin you to the end. retriggers are completly pointless in most games unless its "your time".
also have to take the RTP into consideration, depending how much your down, how much the game is down that time of day, how the RTP on the whole site is. its all taken into consideration. my personal opinion is the sites choose if your a winner or not that day. but that is MY opinion.