If you're like me, part of being a pilot is aspiring to own an aircraft. There's something to be said for knowing you have access to an aircraft of your choice, at any time on any day. It's nice to be intimately familiar with it's handling qualities and avionics (or lack thereof,) and to know exactly how it's been treated by the last person to fly it. Aircraft ownership is a wonderful thing, but it's not without its difficulties. Taking care of an aircraft is a lot of work and it's relatively expensive.
Cost is probably the most commonly-blamed reason for the overall decrease in the number of pilots right now. Owning an airplane has the potential to decrease the hourly cost of flying, but only if you plan on spending a great deal of money on flying in a given year.
If you're looking for affordable aviation and aspire to own an aircraft, then a flying club might be a great way for you to go. If you're interested, AOPA just released a great set of resources for starting a flying club.