What's amazing about Spaceship Earth is that it is giant and perfectly round. If the bottom part is unnecessarily obstructed, people are less able to appreciate that it's not just another big dome on a planet that's had giant domes for many centuries now.
And am I the only who who is tired of those ugly tribute stones? I think having those was a greedy mistake.
Then again, letting people keep some ashes in the grave yards in and outside of the Haunted Mansion makes perfect sense to me.