Weather Sealing is a Gimmick.

I see you don't own any weathersealed bodies. Maybe it's not important to you. Maybe you only shoot in very good conditions. I tend to get out in nature a lot, in somewhat damp hardwood forests where I live, so it's a bonus for me.

Weathersealing means the manufacturer has made some attempt to keep moisture out. Yes, it does require both body and lenses be sealed. No, it does not mean you can shoot under water.

More than one person has lost a camera when they were shooting in humid conditions, put the camera in the bag, the humid air inside condensed, and the next time the camera was powered up - no function.

I've read a couple of tales of woe where someone was shooting at a beach, an unexpected wave caught them - no more camera.

Weathersealing also keeps dust out, if one is shooting where there is a lot of fine dust, like a desert.

My personal experience... was crossing a creek with my old Oly E1 and 14-54 lens, both weathersealed. Slid on an algae covered rock, over I went, and the camera in my hand was briefly put about a foot under water. It came up shooting, no worse for the experience.

I also left my EM5, mounted on a Nikkor 400 3.5 (not weathersealed) on a tripod outside overnight, when I was shooting moon shots and forgot to bring it back in. The next morning, it was drenched with heavy beads of dew. I was careful, due to the non weathersealed lens - dried it off with paper towels. It powered right up, no problem.

It is not a gimmick. It is an extra safety margin, that you probably won't lose the camera if the weather isn't perfect. It has saved me twice already, so I like it.