It used to be true but in 2000 Selective Availability was disabled which made the civilian signal just as precise. This is basically why GPS took off around that time despite having been in operation for two decades at that point.
It's just one of many whys. Differential GPS was widely available and it gave cm-level positioning precision.
Equally if not more important why was your good old hardware minituarization and its cost reduction. In the late 90s a decent GPS reciever was still a size of thick book and cost prohibitively.
Again, coupled with differential corrections (available for free over radio) the resulting precision was in centimeter range. The reason it wasn't used was the physical size and cost (for hand-held navigation) and the lack of supporting hardware in cars (no user-facing on-board systems with screens and UI).
SA was _not_ the reason for the lack of consumer-level GPS adoption.
In my experience using DGPS around 2000, most of the DGPS sources were near the coasts and operated by the Coast Guard. There were a few scattered transmitters here and there, certainly not enough to provide the kind of coverage we now enjoy.
