There are many reasons for getting a laptop,
Mobility is only one factor.
Users who only do word processing, surfing internet, check email, which do not require powerful processor and low maintenance, NB will be their best bet.
No cable, nothing to hook up basically
Also if you look at some entry level Notebook/Laptop/Netbook, the cost is lower than desktop.
Tablet is getting very popular and it is impacting both Notebook and Desktop market.
