I never understood people that take shower with their watches. What's the point?
Aren't you gonna scrub your skin under watch? Why don't you wear glasses while taking a shower while you're at it. Or sleep with your work clothes including socks and boots.
It's a matter of convenience. Once you strap it on, you never have to worry about it again, unless it stops working.
The same is true for the reason you remove glasses, and clothes before sleep -- comfort and convenience. Glasses have to be cleaned after they have been gotten wet to avoid water spots in your vision, so that generally creates more problems than it's worth, but I do know some people with very bad eyesight who wear glasses in the shower, or they wouldn't even be able to find the soap when they dropped it. Wearing uncomfortable footwear in bed would not be comfortable and detrimental to the sleep process. The same from bulky work clothing. Besides that the clothes would get wrinkled and transfer dirt to the bedding, again making it more trouble than it's worth. Some people do wear socks and softer pajamas to bed, and I'm sure a few do wear workboots to bed if they are in environments where needing to get up suddenly at night and be immediately alert and ready to move (say a soldier in a war zone).
For me, I wore a watch 24/7 for about a decade. It was a light titanium Citizen chronograph that worked in all settings. I could work out in it, shower in it without worrying about it getting stolen in the locker room, dropping it on the hard tile floor, or misplacing it. It was loose enough on my wrist to allow me to move it enough in either direction to wash beneath it. I could swim in it, I could sit in the hot tub in it, etc. I never had to worry about it ever. I never found it particularly uncomfortable in bed, certainly far more comfortable than any pajamas I've ever worn which tend to bunch and get caught up when you turn during the night, yet millions of people wear some form of clothing to bed.
And as others have pointed out, the Watch offers even more compelling reasons never to take it off, because it can be used to answer that all important phone call, text, or e-mail without exposing your iPhone to water or accidents (I had a friend who knocked his iPhone into the toilet when he reached for it from the shower to take his bosses call). Playing with your children in the pool, while working is priceless.
But that's not an option yet for the Watch, despite the fact I've never seen a watch priced over $350 that wasn't able to withstand IPX 8 30 meters -- a market Apple appears to be competing head to head with unlike their cheaper smart watch competitors.
