Weather sealed/proof DSLR/mirrorless.

After thinking for a while, I wonder why weather proofing is not more commonplace in cameras considering their usage. Seems like only the upper end DSLRs are weather sealed/proof. Maybe Pentax models? I think some high end micro 4/3rds are too, but I don't know if they are truly weather sealed compared to the big boys. Any recommendations/feedback without having to spend $$$ on high end DSLR/m43rds?

There's the waterproof Nikon AW-1, but it's not in the same class as other ILCs/mirrorless in sensor size, I think.