It is difficult because of the way Steem is designed. There is a account creation fee for creating Steem accounts. It is currently set at 0.1 Steem. But you need to have 30 times that amount to create an account. 30 times 0.1 equals to 3. So, 3 Steem is needed to create new Steem accounts.
3 Steem is worth less than three dollars at the time of writing this post. Steem accounts can only be created by other Steem accounts and this fee is transferred from the creator Steem account to the newly created Steem account.
If a new user doesn't know anyone who has a Steem account, it will be very hard for him to create one for himself. He would either have to buy an account from services that sell accounts or use the annoying signup process of Steemit (even if he does it, there is no guarantee his account will be approved).
Even if he has friends with Steem accounts, there is a possibility that his friend doesn't know how to create new accounts. Creating new accounts require a little bit geeky knowledge and understanding of Steemconnect's account creation tool. I failed at creating new Steem accounts when I first tried it.
I then had to search around the web a little to figure out what I did wrong. This is why I think many of the average Steem users don't know how to create new accounts.
Due to the above stated reasons, creating Steem accounts is quite difficult for people who want to join the platform.