I rarely need a first aid kit when I ride, but the odd time I have needed it [for someone else] I was glad to have it with me. I’m no good at remembering to move F/A kits between packs and bags. So I bought 4 or 5 of these small kits and I leave one in each pack or bag I use regularly. They are cheap and they’ll last a long time before needing replacement so they are a good investment.
I also have a large first aid kit in my truck.
Knowing how to do CPR is an essential skill you need to go with your first aid kit.