It may not be necessary, but it's something you can do pretty much any time. You don't need to change or pull out heavy stuff, for example those grippers are very small and I just leave them on my coffee table or nearby and use them when I'm watching a movie or whatever.
Also, I exercise my grip by carrying 12-packs of beer (cans) around and out of the store by gripping the sides of the box. I probably do this exercise more than I should, though.

But there are plenty of opportunities in everyday life to do things the harder way and develop your grip.