you anyway have to buy A THIRD external footswitch
Uh – you don't have to buy any foot switches, at all.
If for any reason, you want extra switches, you'll probably be glad that they are made available. If you don't, you won't care.
Some people are very tight on space on their pedalboards and appreciate the H9's "compact" footprint, especially if they have more than one. And again, others are not concerned.
Horses and courses.