Where are you getting this assumption that updates bloat and slow your system to a crawl? They certainly do not! If your hard drive is full, I would recommend that you buy a new one that has adequate space. My home computer has a 3TB drive that's future proofed for anything I need.
Also if my car dealer said he needed me to bring in my car to upgrade my car radio, tires, steering wheel, whatever for free - I would be there in no time flat. I would be grateful that they are giving me new products for free or fixing existing issues.
And Windows 8.1 brings a lot more features than just cloud storage like being able to search everywhere. Even a lot of the updates in Windows 8.1 update 1 brought a lot of changes that people who hated Windows 8 wanted. But you can only see those changes with Windows 8.1 as Windows 8 is no longer supported which is why they are pushing it to you.