Pressing the PTT button is rather easier than fumbling around with a mobile phone trying to send an SMS. And of course, as we all know, the latter would interfere with the aircraft's navigation systems and you'd end up in the wrong place!
In South Eastern France, it is CAA policy to ensure that as many airfields as possible have pilot controlled lighting. They deal with the integrity issue by checking the bulbs work once in a while, and installing a backup generator. They then mess it up by reserving night operations to locally based aircaft in too many places, but at least you can arrive back home without problems.