It's not even to look better necessarily, just that back when internet services were starting out it was far more legible to advertise in kilobit/megabit
it is hard enough getting the average user to go from reading MB/s to Mbps and now they are just getting used to it we will confuse them on GB/s vs Gbps
Starlink's primary audience is folks out in the sticks getting ignored by landline ISPs which were paid billions by the government to not ignore folks out in the sticks