As for why they're low pressure, consider the following points:
- They tend to be shorter, and participants are fewer.
- For QSO parties and country-sponsored contests you likely can point all your antennas at the start of the contest and leave them there.
- You can take time off without losing many points since there is a smaller pool of stations to contact and propagation may not be there for part of the contest.
- There are many stations from the sponsoring region to test propagation and antennas.
- With all antennas pointing the same direction you can easily compare relative performance at different times (band opening, mid opening, band closing), knowledge you can put to good use at other times.
- Compare fixed yagis with rotatable yagis by seeing how many degrees a yagi can be off the side of the path until it matches a fixed yagi to that region. From here small European contests are most useful since it is common for fixed yagis to be pointed at Europe.
- I like to call the really weak stations to see how often I can complete the QSO. This is good practice for those running low power or QRP, and for QRO operators who get many weak callers during runs. In the small contests there is less rush to move on to the next QSO.
At the other end of the spectrum are what I call zombie contests. These are smaller contests that, although still sponsored, have low activity. There is little or no promotion within the sponsor's country or region, thus only the diehards bother to participate. Like zombies these contests somehow continue to shuffle along year after year despite being as good as dead.
I won't name any of these contests to avoid annoying the guilty parties. Some are so dead that you can work few of the sponsoring region multipliers because no one is active. When the 3830 reports repeatedly note a lack of sponsoring region activity you know that it's a zombie contest. No one enjoys a zombie contest so those stations are unlikely to return next year.
Many zombie contests need to die. However some can be jolted back to life with the backing of an enthusiastic group or club. As for ARRL Field Day and other contests clubs can turn the event into a group activity with a combination of organization, recognizing participation, putting fence sitters in front of radios, and even use gimmicks such as special calls for extra points. It can be done. In the US the California and Florida QSO parties are good examples of small contests with enthusiastic backing and lots of activity.
But are there simply too many small contests on the calendar? Not really since there is no need to participate in all of them. Pick those that appeal to you or take place a week or two before a major contest and go for it. Try one and discover how much fun (and valuable) it can be.