I started playing DnD when BX first came out. And I was probably a tad too young at the time, and our group never used Wandering Monster checks or had a Mapper. Even the group I fell in with as an adult seemed to have come from a similar background, these ideas were just ignored. Years of playing 3e only solidified this approach.
These ideas are pretty central to the ORS playstyle and attempts to introduce them have not worked so well. As DM, I would constantly forget to roll for wandering monsters, and sometimes when I remembered, I would sometimes ignore the results of a roll (against my better judgement) to keep the game flowing.
As far as mapping went, I could see players tune out when I would have to describe a quirk in a rooms layout that made it tough to relate to the mapping player.
Not sure if any others have had a similar story, but just in case, I wanted to share a couple tweaks that brought both of these back into my games nicely with good player buy in and results, and it was simply to switch around who was doing what.
For wandering monster checks, the players roll. This ends up making it easier to integrate with the standard exploration procedure, players see clearly the consequences of their actions and danger level of the area. It builds player trust (the DM is not sicking grudge monsters on us) and even heightens the tension as everyone watches that roll carefully, rather than it being something in the background the DM is doing behind the screen.
For mapping, as long as the party has a dedicated mapper assigned with enough light and writing supplies in hand, and moving at normal exploration speed, I draw the maps as we go, all as part of the area descriptions. This also plays out nicely with the prior rule, as each square can be easily tracked against the party movement rate for each turn, for purposes of handling light sources and wandering monster checks.
This has worked well for me, and might be something to try with your group if you are having similar issues.
Now, any ideas how many pages of mapping 1oz of ink is good for?