Old-school D&D systems in general, and "non-Advanced" versions in particular, have a bit of a reputation for slow advancement and lethality (not necessarily in that order). How many 1st level corpses lie in the Caves of Chaos? How many brothers, sisters, sons, or cousins of the original PC had to take up the mantle before one of them made it to 2nd, or even 3rd (!) level? Some players are frustrated by this, and that's a fair point. The PC that perseveres may one day not only graduate from the red book to the blue, but eventually reach the airy realms of 9th+ level. A world where strongholds and wizard's towers may be built, followers start following, and the PC can move from murder hobo to robber baron.
Of course the party might choose to continue their wandering ways, slaying bigger and badder monsters and taking bigger and cooler stuff. Perhaps they need to gather a bit more hard coin before they can afford that moat for the castle. Maybe they're trying to impress the king so they can receive a title and fiefdom. In any case, a campaign that manages to get to this point is likely to see the dungeon crawl for crawling's sake as getting a bit stale. Players may well be ready for a new kind of challenge.
I confess that I've never run a BX game that got to this level. The closest it ever came was having a couple of Labyrinth Lord PCs reach 5th-6th level by the end of B10: Night's Dark Terror. Back in the day, our 1st edition game saw name level PCs and strongholds, etc. but we were pretty monty haul as kids & teens in the 80s. We hardly explored the political or military aspects that could have been integrated into the campaign.
For the next few posts, I plan on taking a look at the "name level PC" rules in BX, as well as some of the secondary rules associated with this level of play.