Listen to a commercial station, any of the popular music ones.
Whilst you're listening write down the tracks as they're played, then when you hear it again, cross it out. I'm willing to bet that after 4 hours every track will have been played at least twice.
Now listen to Radio Two, it'll take at least a week before every track has been played twice.
The Commercial stations cater to the lowest common denominator, their only concern is advertising revenue, so they carry out audience research and only play the music that the audience wants to listen to, unfortunately that's all they play, the same tracks over and over and over again. Duffy's Mercy is still on heavy rotation on many ILR stations, and it's almost 12 months old.
We used to have a fantastic local commercial station, The Revolution, it played a fantastic mix of current indie, early 90's Manchester dance rock & northern soul classics. All was well fro 2 years until Steve Penk decided to buy the station and turn it into a sub Magic Radio clone over night, and the listeners left in droves.
The local BBC stations provide a valuable, voice radio resource supporting the local community. Many ILR stations actually syndicate many programs and only the daytime shows are local.
Any comments about BBC quality do not include Radio 1, which is a stain on the network...