Obviously we shouldn't pretend sat phones from Garmin and others haven't existed for decades, but Starlink direct to cell is very different. First, as others have mentioned, traditional sat phones requires dedicated hardware with a chonky antenna; this works with normal cellphones, which means order of magnitude higher adoption. Maybe more fundamentally, the satellites that existing sat phones use are in much higher orbits so there is irreducible latency (due to speed of light) and bandwidth costs that LEO Starlink sats will likely crush in the next few years.