Some of the reasons you might choose not to compete are.
1. Avoid the stress of it all. many pipers might decide never to compete or to stop competing because they can not handle the stress of being compared to there peers. Few pipers are calm when they compete.
2. Some Pipers stop competing after a bad set of results.
3. Time is probably the only reason I have not competed this year. It requires a lot of time to prepare to compete.
Why every piper should try to compete:
1. Competition helps you set goals with deadlines that have to be met.
2. You get objective feedback on how you are playing, the feedback is not bias, such as that of your own or your tutors.
3. You learn to play under pressure and this improves your playing in gigs.
4. Getting to know other pipers. Competing helps you build comradeship with other pipers.
5. A chance to compare yourself to pipers that are better than you and aspire to lift the level of your own playing
6. Pushes you to learn tunes with more attention to detail; timing, grace notes and clarity.
7. A good result can encourage the piper to work even harder,
8. It is the only way to earn the respect of your fellow pipers.
Having written all that I think its time I competed again (its been 7 years)