If you need a bead jack to mount your tires, you had better have it with you when you get a flat or you are going to be stuck.
True. MIne weighs almost 3 oz, so it's not a great burden - but I use a rack trunk to hold a lot of stuff that others - probably most of BF - don't carry on their rides.
I had one set of tires that the chief mechanic at a successful LBS mounted by hand only after 20 minutes of effort; the tool would have helped him. My thumbs are arthritic; the tool is essential for me.
One needs to develop some technique to use it effectively; the better the technique, the easier it is to mount a tire.