For phones that infrastructure is just so much more costly since it needs near constant replacement with newer tech. 5G is far from completely rolled out and the next project looks to be dismantling GSM and 3G after that it won’t be long till 6G. Meanwhile Fiber is all but ubiquitous by now, hell several vacation homes in the extended family has fiber ny now and the cables won’t need to be switched for a long time I reckon, I’m betting 30 years at least of only needing to change the switches every 10 or so years, which is infinitely cheaper and easier than building/replacing a mobile network mast.