I have another thread on this very issue.
I travel all over the country and am on the road 80%+ per year so I think I have a pretty decent view of how ATT is and I've been less than pleased at the substantial decline in service availability in many of the places I go. And it isn't because of low signal strength either as I often get no response even with 4-5 bars.
It's likely a combination of things but it adds up to too many people doing too much high data streaming. 1.5 years ago when ATT was actually pretty good there were a very similar number of smartphone customers as we've been at replacement levels for a couple years, and the only thing that makes sense is that more people are eating more data.
I've complained about data hogs, but they can't be the only thing causes this as there numbers haven't really gone up much in the last couple years. So, if data hogs can't be the sole problem then that pretty much leaves most everyone else eating more data. I know that the average user a couple years ago ate less than 500MB/month and I have to believe that the average is well past 1GB/month and could be quite a bit higher than that.
Netflix's et al have dramatically increased data use, but the pipeline supplying the data hasn't been keeping up and can't really keep up -- the technology just isn't there yet.
I heard just a couple weeks ago that for the first time the total data transmitted via cellular will exceed cable to home/business. It's not hard to increase data capacity to the home or business all you need to do is add another fiber or cable but you can't really do that with cellular.
Brian