Div 1 users participate so less in rated contests ?
I do not think so, I have seen many div 1 users participate in almost every contest.
you can see many Div 2 coders not participating regularly.
Even if they do most of them participate only in long challenges not in short. How does it increases one’s skills ?
Long challenges ask questions related to CP. I all the long challenges I participated , I found hard CP questions , much harder than short challenges. Long challenges is a good way to learn CP , I have learned CP by participating in long challenges .
I do participate in short challenges ( in a team or individual ). I have not achieved much but been finalists in a few good competitions.
And I ask all the coders who do not consider Long challenges as a part of CP . Please do participate in long challenges and become a 7 star or among the top 10 in world (because it is too easy for them , you might solve all the 8 questions in 2.5 or 3 hrs).