I mean literally, whatever you do don't go overboard. There's a shit ton of crabs down there!!!

Maybe it's because they don't have a big bulbous ass full of death net fluid and baby spiders?

I think perhaps, a crabs chitinous exoskelton is cool and charming, whereas a spiders is hairy and gross.
Also theres the issue of scale, crabs are bigger, stuff that I can carelessly squish freaks me out.. And I know small crabs can be smaller than big spiders, but a small crab is a small example of a normally big thing whereas a big spider is a giant example of a normally small thing! Makes total sense!

Spiders tend to move a lot faster it seems, also crabs sideways walking is quite disarming

Black Widows & Brown Recluses'? Deadly & possibly under your bed.

Crabs? Who has even been killed by a sand crab? Also, probably not lurking in the dark corners of your house.... Just saying.

Spiders are venomous BDSM freaks that jellify the innards of insects and sucking them out hollow.

Crabs are adorable robots of the sea that eat ocean garbage and walk in circles.

Also, a crab can pull off a top hat and monocle.

Show me one spider that would look good in a top hat and monocle.

Oh, wait. Jumping spiders.

Of course, jumping spiders are more puppy than spider, anyway.

Or a stingray.