I did a couple speedtests with Verizon Xlte and it used up almost 1GB of data!
Will verizon/at&t exclude speedtests from counting against data like T-Mobile?
It's unlikely. Verizon and AT&T also count streaming music services against their data allotments, unlike T-Mobile (which does not). Verizon and AT&T also don't seem all that much in a rush to deploy WiFi calling either, or a referral program, nor are they motivated to really lower their prices much, at all, nor will they pay your ETF if you switch from another carrier... or offer unlimited data on smartphone plans... all things T-Mobile currently does.
Bottom line is: Verizon and AT&T are largely a duopoly, with T-Mobile a distant fourth with less than half the customers of either of them. T-Mobile has years of bad reputation to overcome as a poorly-run network, and have a lot of ground to gain, so they are a lot more motivated to do these sorts of things.
To T-Mobile's credit: They've really turned their network around in most places, though coverage is still lacking in many rural areas. And they've been gaining a LOT of new customers lately, more than any other US carrier in the past few quarters (myself included). There's a good chance they'll become third in size in the US by Thanksgiving 2014, leaving Sprint in the dust.
If you don't care what kind of speed you're getting, then it probably won't make any difference but for those that love to check your speed often like me, I find that it wastes too much of your data way too quick, especially when you have 50+ mbps speeds.
It's just not in Verizon and AT&T's interests to do anything to encourage its users to test speeds frequently. Maybe a test now and then, once or twice a month, under favorable conditions. But their business model is based on extracting as much money from heavy data users as they can. Whether that heavy use is from running speed tests all day, or something more worthwhile, it doesn't matter to them.
Don't get me wrong: I'm not defending AT&T or Verizon on this. Personally I feel their data plans are highway robbery, particularly for individual users, and that their elimination of unlimited plans is motivated more on greed than on actual network management needs. But that's one of the reasons they no longer get my money.
Q&A
Q. Why do I continue to do speedtests if I already receive 50+ mbps speeds?
A. Because it's fun and I want to see if I can hit 100 mbps download. So far the max download speed I've gotten was 85 mbps.
Fair enough. But you have to understand that on AT&T and Verizon at least, that "fun" will cost you if you have too much of it. If you want to run speed tests to your heart's content, you'll have to go to T-Mobile.