This is a good point, I'm not entirely sure if it's possible or feasible.Is it even feasible to get a rail line close to Universal? No doubt there’s some exclusivity in the agreement but I don’t even know if you could get to current UOR if you tried without buying out businesses and hotels to bulldoze.
And for the Convention Center - a good number of those people are expensing their Ubers and taxis so it holds less appeal.
In the past, airport transportation directly to Disney has led to people being "trapped" on Disney property
Of course, with the advent of Uber and Lyft I suppose that's a bit different than 2008
Still though, that's an extra cost to an already expensive vacation