AT&T, Verizon & Sprint are massive companies that comprise the majority of business in the USA.
They are free to do what they want, when they want. So... don't ever think that what is true today will be tomorrow. Nothing is forever, and nothing is set in stone.
Sprint just increased their ETF to $350 for the iPhone. Does that make them a bad carrier? No. It's the nature of business. What one company does, will be reflected by the others sooner or later.
AT&T haters conveniently overlooked the fact that it was Verizon that was the first to raise ETF Fees to $350 while AT&T's ETF was still just $150 many months ago. So naturally within months of the move by Verizon, AT&T followed and increased their ETF to $350.
The Point? It's the cellar industry people and none are here to make your life easy by keeping your costs to a minimum. They are here to get maximum return on their investment. It's just business.