Because players are used to having it easy and are annoyed at the slightest infusion of difficulty. Why should we have to use our brains to figure out solutions when we could have had it easy!

In all practically, this just makes using alts to tap the summon much more difficult as well as punish players who are late, as it's now fairly difficult to just leave the summon up for 20 min so everyone gets to tap it. Nope, now you have to be active and on time.