Truth be told, I don’t really like doing it. But I want to have a testing kit next to my bed side so I don’t ever have to get up again when EH can’t find his actual testing kit. 
And really the most useful time is pre CGM, when we would be on long road trips. He usually drives, and I have tested his blood sugar while he was driving and that is handy. But having a kit by my bed wouldn’t really help at that point! 
I think many of the things I tend to do in regards to EH’s diabetes are actually there to make my life nicer. Which is incredibly selfish, but true. I worry less if I know we have a source of sugar. I worry less if I know he could do a fingerstick and identify what his blood sugar actually is. I worry less if we have a supply of insulin in the fridge. And the suitcase. And the bag. And a spare pod. Even though we are really often flying by the seat of our pants, I have developed some failsafes over the years. He’d be fine with one testing kit and not a lot of backup supplies. But I have spent enough vacation waiting in line at Cosco pharmacy to get missing D prescriptions that I never need to do that again. 