To start, aircon is an incredible racket in general a lot of the time. Good companies exist, but lots of others, especially in the USA, have been bought up by big holding companies and converted in to profit maximization new-system sales machines. Techs get paid pretty poorly, and helpers get paid worse than mcdonalds/target in a lot of areas. There's not much financial incentive for someone to get really good at understanding residential a/c systems for repair/diagnosis anymore in most places.
Then to your tablet question: even on simple non-zoned systems, lots of manufacturers have totally moved away from oldschool thermostats that have simple fan/compressor/power/etc.. wires, in favor of "communicating" systems. "Communicating" means there's a proprietary protocol that their thermostats, control boards, and other misc electronics in compressor/condenser assemblies speak; for which there is no standard. A handful of modern advancements kind of necessitate this, such as variable speed compressors (yea, you could totally control that with normal electrical hardware, but....no one cares).
Couple all that with people willing to pay damn near anything to cool off when its 97f outside, and you end up where we are today.