You get priority to be summoned plus you don't need to use a sign or orb which will most likely get you into some other form of multiplayer. Getting summoned without any sign, orb or covenant item is extremely rare so this is the best way to guarantee this as the only form of multiplayer.
If you DO want to be summoned for this covenant without equipping it, you can put down a password sign somewhere to avoid being summoned by other folks.
Re: august 21, I get summoned pretty often if I hang out near the spear monument at ~sl90. Definitely a "have on in the background while doing something else" kinda covenant but I would say I usually get a hit every 5-10 minutes at most, usually more often.