For those complaining that "it looks awful" let's review the mantra, since everyone likes to pull out the list on so many other issues:
Safety, Courtesy, Show, Efficiency
Certainly the umbrellas help shade the people under them in the sun, reducing stress from heat, along with blocking some of the rays to reduce sunburn. That seems to promote guest Safety.
And certainly Disney isn't required to provide these to guests, but it's a nice gesture for those who decide to wait in line (arguments on whether or not its worth waiting for aside), and I'm sure is nice in the event its raining. That seems to be a Courtesy for guests.
Seems like Disney is putting Safety and Courtesy first. And handing out umbrellas for guest's temporary use doesn't seem to put Efficiency above any of the other three, so I think we're all clear here.