"We" in the UK seem to have got that right, there is legislation requiring ISPs (both residential and mobile) to permit other companies to use their infrastructure for a reasonable cost, so you get big names like EE who provide the typical 24 month contract with "free" handset type deals, but you also get smaller companies using their network. SIM only contracts from the big companies are awful value (say £20/month), the same deal from a 3rd party using the same network is typically <£10/month.