The reason late registration goes on for so many hours is so ACR can put larger guaranteed prize pools on their tournaments... and larger guarantees means they attract more players, and attracting more players means the site generates more rake for themselves.
Having many levels of late registration is for sure a money maker for poker sites, because it allow more people to enter or reenter late. But the main reason, why some tournaments on ACR have such long late registration periods, are long blind intervals. For instance at 2 pm CET there is a 2,2$ 800 guarantied MTT with 15 minute blind intervals during late registration and 16 levels of late registration = 4 hours and 20 minutes of late registration due to the breaks.
And I just dont see, how such a tournament is a good money maker for the site. The slow blinds mean, people play longer on average, and if they busted faster, they would probably buy into another tournament. After all this is why, some people beleive, the RNGs are rigged to favour the big stack.
And in my opinion each player buying into more tournaments would more than compensate for the fact, that a faster tournament with 8 or 10 minute blind intervals might need to have a lower guaranti like say 500$. Sure there might be some players, who look very much at the size of the guaranty. But there are many others like you or myself, who dont want to potentially play for up to 8-10 hours, when we are only playing for 2,2$, regardless if the guaranty is 500$ or 800$.
ACR is also pretty alone in the business with these very slow structures. On
pokerstars only the "daily marathon" and some special events during series like the current "Winter Series" run that slow. Everything else is 10 minutes for the vast majority of "regular speed" tournaments, and even Sunday Million only has 12 minute blinds until the final table or something. And when
888 Poker changed their tournament schedule last year, they made most of the smaller buyin tournaments 8 minute blind intervals and shortened late registration to 70 minutes.
So if these very slow tournaments are a brilliant money maker, then everyone else in the business are missing out, and only ACR have seen the light. And I guess, its probably more likely, its the other way around. I dont know, how the tournament schedule was on ACR before, like when this post was made in 2020. But right now most of the tournaments have 8-12 minute blind levels, and there are only a few of those left with 15 minute blind levels. And when I played the said 2 pm CET 2,2$ event, it ran with an overlay despite 4 hours and 20 minutes of late registation, so ACR did not make a single dollar on it.
ACR is also currently promoting their "on demand" SnGs, which are turbos with 5 minute blind intervals. So I guess, faster games are after all more profitable for poker sites, and that even ACR has come around to realise this. And for the meantime people playing there just need to look at the structure before buying in, and personally I am probably not going to play that 2,2$ tournament again. Or if I do, it will be in the form of a last minute registration, if I spot a potential overlay