We think that the end portal is a gateway not just to the end itself but to minecrafts endgame content. We fear that placing the portal at spawn will ruin new players' experience in the same way as kits or "back" command do. we hope this issue alone will be enough to change your mind, but If not, here's some more arguments on the matter. First of all, It will help not the players, wanting to play on a regular basis, but people coming with only intent in griefing the end terrain. Secondly, Not having the end portal at spawn will considerably reduce the amount of times the end gets raided which would greatly ease duty of helpers and other staff as well as improving all players' experience.