In my opinion, pygame is fairly easy to learn/use. This is a double edged sword when it comes to how it looks from the outside. Tools that are hard to use generally require very dedicated people to be able to be productive with them at all. By the time a developer has jumped through the hurdles to get started, assuming that development does get easier as time goes on, said developer might be more likely to have the dedication required to finish a game. On the other hand, with something like python/pygame, getting started might be so easy as to delude someone into thinking that finishing a game will now magically be "easy" because the tool was so easy to learn. I have seen this same problem with other tools that are easy to learn. Getting started may be shorter, but finishing is just as hard as finishing ALWAYS is.
Pyweek is a good example of this. Maybe half of the games in each competition I would say have the potential to be somewhat successful, at least as successful as other indie games could be. But very very few of these games ever get developed further after pyweek. Actually developing one of those games into a full commercial or popular game could take many more months of development even if it seems complete after that week. To sum up, even finishing a game, especially when working alone as most pygame developers do, requires a huge amount of patience and dedication, even though the tool is very good and makes many things easy. The tool is only half the battle in making a good game. My problem is that I basically only work on games with the kind of dedication required during pyweeks, after which I am very lazy and never manage to finish anything. Plus most of my game development energy is put into my mmorpg which is such a huge project I don't know when I will ever finish. If I could spend a few months with the energy I put into each pyweek on a single game, I think I could pump out many at least "able to be successful" games each year. Lord knows I have enough ideas. I just don't have that kind of energy or I use it up in other places. I think many others in the community could do the same. Unfortunately most of us are doing this as a hobby, and we're a small community besides, hence the small amount of "successful" games. However you measure success.
