I can understand 2 days since you might stay at your girlfriend's house or something, but mine already can do 2 days anyway.
However, having a week long charge is also about more than just being able to avoid charging it at night. It also means that the remaining battery capacity (wear, age) will matter less. Is your battery dying, with only 50% of the design capacity left? Who cares, the watch still lasts for days. Not only that - the slow discharge also means that the battery will take ages to even experience reduced capacity.
The Apple Watch, on the other hand, sprints through the battery charges, and will both be completely intolerant to reduced battery capacity and reach reduced battery capacity faster.
... So yeah. It matters.
- you are often in different places from night to nigh (have a lot of friends, a scattered familly, a job on the move, etc).
- you have no brain and forget often to charge your stuff
- you are fed up (or too lazy, or both) to have a 6th stuff to put on your night stand every freaking day
- you want it to be still usable after the battery wears off, and not just half a day like most smart phones after 2 years
- you have a busy party night life
- you work night shifts, or several days in a row without going back home
- you want to put you watch in a drawer, forget about it, and get it back 2 days later, still usable.
You can manage all that with a little preparation, but the point is, you should not have to.
I have a Fitbit and one of the biggest reasons for me is its sleep tracking, which totally doesn't work if, um, I take it off to sleep. As a result I usually end up charging mine while I'm showering.
Unfortunately, if I forget to do that when I hop into the shower in the morning (which easily happens when I haven't had enough sleep and pre-coffee), I very much appreciate that my Fitbit's battery lasts more than a single day.
Can't do that if you're using the watch for sleep tracking.
I've got into the habit of putting mine (an Apple Watch Series 2) on charge when I get up and leaving it there till I'm about to leave.
Other than the odd top-up (if I've been using the Workout app and thus the heart rate sensor), no problems. More battery life would be good though - if it used to be worse with the original AW, it's not hard to see how that would be a problem.
I charge my Pebble once a week. Before that, wearing a bog-standard digital watch, I took it off ~never.
This is where you differ from many (probably most?) watch wearers.
I have a Pebble. My SO also has a Pebble. We can sleep together just fine, without taking them off.
Which is a tiny tiny niche
shrug
My old non-smart watch had battery that lasted 2 years, and generally I never took it of for sleeping.
Was kind of gross tbh.
I spend more often than not 3-4 days away from power in a given week.
I personally like watch that is low maintenance, I don't want to worry about having it charged. As others mentioned you can use watch to wake you up. I also use my pebble to track my sleep.
Another thing that is often ignored is that if battery doesn't need to be frequently charged it will also last longer (battery life is measured in charging cycles).
Sadly this might be the reason why Pebble has issues, their watch is quite good, so when they released second version of Pebble Time, I decided not to buy it because I was still happy with mine that I got 1.5 years ago.
I find that the only time I don't wear my Pebble Time is when I am having a shower and in those 10-15 minutes I can fully top up the charge on the PT, which I find is a killer feature. Basically, its more/less constantly charged, I wish other Watches (Android, Apple) would implement 'fast charging' to replicate this feature, as I hate having to think about charging any device.