Depends on your project timeline, scope and your client.
If you have a lot of time, a fat budget and a patient client you may not want or need a framework of any kind. In an ideal world you can scaffold your own projects, or provide build systems and base operablilty custom to the client. however you will find most of the time that you never have all three of these gifts, rather you have two, and need to make up for the lack of the other... be it time, scope, or client.
Often frameworks are chosen when you realise the budget is low or the timescale minimal - or that the scope is much larger than you prevously thought.... at this time a framework can come and shed some this load for you, providing you with a set of predifiened guidelines/patterns than can help you shortcut parts of the project dramatically - people get used to these shortcuts very fast and find they have a favourite framework for certain tasks - often you will find this leads the decision of what framework to use (the developers familiarity with it) more expereienced developers have tried more framework and therefore often have a greater forsight as to which is better to help us get to particular goals. Despite perhaps not needing a framework for a project at least one is often chosen to help get the ball rolling so people involved in the project can see results quickly.
Getting used ot certain build patterns can help you pump out applications very quickly, some may argue why not use a framework if it gives you this kind of head start. for personal projects I nearly always use somekind of framework because in a personal project you are oftena one man band so the time saved by using becomes invaluable - comparatively there is lots of cool stuff to learn if you can relaese yourself from some framework shackles, and code some of those parts yourself (Routing, Templating etc)