My impression is that in the bad old days the phone service offered by government PTT monopolies was expensive and inefficient, with waiting lists for lines, slow/bad quality connections, etc. Infrastructure was way behind that in the US. That caused a great appetite for the capabilities offered by new technologies, such as mobile, as well as their ability as an alternative to the inadequate landline service, and the growth rate for mobile service was extremely high, as a result.
In the US, the landline network has long been pretty affordable and available, so mobile service was targeted (initially) at those segments who valued mobility enough to pay a premium, rather than as a landline replacement or substitute.
There was a very high growth rate, and to sustain that growth U.S. carriers needed to target not only doctors and lawyers, but also drivers of pickup trucks and eventually schoolkids. A high level of competition, spurred by FCC decisions, has caused marginal rates to continually decline, so carriers need to expand usage and customer base.
As a result, many US young people are so used to using the cellphone that they don't bother to have a landline. At my daughter's college, every dorm room has a landline phone. Neither my daughter nor I have any idea what the number is. She uses her cellphone exclusively. Because of the wireless companies' nationwide calling plans, the kids in her college can keep numbers from their home areas, often on family calling plans, and call each other without "long distance" charges, even though two students may be calling across campus from phones with area codes ranging from Alaska to Florida.
Europe doesn't offer quite the same level of free calling across borders, but the cellphone often is less expensive to use than landlines for making calls. (However, the regulations in Europe also impose a surcharge on landline calls to cellphones.)
Michael D. Sullivan Bethesda, MD (USA) (To reply, change example.invalid to com in the address.)