Mostly because there are so many that, combined with the ultra-low speed limit and the long stops at every cross street, it can take a very long time to get down the Mall.What is so wrong with buses, especially the hybrids they run now? This no buses on the Mall call has always seemed a bit classist to me.
If Nicollet Mall is to be the retail center of the city we want to bring people there!
I mean, today, I rode an 18 from the Central Library to Nicollet/Franklin and it took twenty minutes, a lot of which was because we kept getting stopped behind another bus waiting to get to the stop. Same story when I rode a 17 back; an absolute crawl the whole way (though not as long as the first ride). That's to say nothing of the taxis that are still allowed on Nicollet, which in my experience seem to go out of their way to get in the way of the buses.
And just generally, I think for the kind of uses that people envision for Nicollet (open-air restaurants, large crowds of shoppers, big communal gathering areas) there's a point where more vehicles can have a dampening effect. Of course we want more people on the Mall, but at the same time, we want the Mall to seem pleasant and pedestrian-focused. Hybrid buses help a lot (I've never noticed diesel fumes personally), but they aren't a panacea either.
This idea would have so many operational (not to mention liability) issues.In fact, just save the money, skip the streetcar, and have the buses mingle with pedestrians.