There's a reason people didn't lug around spears most of the time. The one I own is 1.8m long, it's a big stick. Even on a sling, it's going to constantly snag on everything (and always threaten to poke someone nearby, not exactly fun) Do you want to walk (or sometimes even crawl) through confined spaces with a spear and a shield? Especially when there's no reason to expect any fighting (why would there be? -- it's just some old ruins, the worst thing that can happen is a bunch of vagrants hiding there, and diplomacy tends to work on those)
Can it all be hand-waived? Sure. But then spears/longer polearms either become utterly overpowered or have to be nerfed to make all other weapons viable, there's just no other way around it.
Sorry, but, who didn't lug spears around most of the time? Nearly anyone who was headed out into the wilderness took a spear, starting all the way back in paleolithic times all the way up to Roman era and, depending on the part of the world, right up to the advent of gun powder weapons. Carrying a spear was FAAAAR more common than carrying a sword. Swords are absolutely crap weapons against anything that isn't a human. Who would you put money on against a charging boar - man with sword or man with spear?
I'm going to point out that the specifics of your particular game are not terribly relevant here. Frankly, I don't really care what you are doing at your table, any more than you care about what I'm doing at mine.
Fighters almost always carry shields, even if they have swords, so, that's moot. And, there are 6 foot swords in D&D. Which is the same length as your spear. I can't imagine that it's all that much different trying to crawl around with a four foot sword on my hip or a six foot spear strapped to my back. They are likely both going to be rather difficult for crawling around in.
Just because a weapon might be inconvenient in one fairly specific location doesn't really matter all that much. Overall? Spears should be used FAR more in the game than they are. But, since spears suck and virtually none of the cool weapons are spears plus the fandom love swords FARRRR too much to ever give them up, that means that spears will virtually never be used by PC's.
I mean, good grief in forty years of gaming I cannot recall a single fighter type that focused on spears. Not one. That's how crap spears are in D&D.