If you're not losing weight with the amount of activity you're currently doing, then you need to do more. There's nothing special about exactly 10,000, which was based on marketing not science.

Not at all. It’s a good number to shoot for and there are benefits- you have a daily habit, the length of time required will give you some destressing time, if you go over it feels great, etc. But if you do less, that’s ok too. If you set a daily goal of 6k- that’s 6k more than an absolute couch potato. I have plenty of days where I may only get 4k. That’s ok, I’ll make it up the next couple days.

It’s not mandatory but for me it’s more of a habit, I run and I quickly clock 10K or more steps per day through running and of course through moving around during the course of the day.

I think theyre for those not actively exercising.

Nope. I will say one thing walking does help stimulate is your lymphatic system. If you don’t feel like walking, do some calf raises a few times through out the day to get stuff flowing