Many lawyers don't do this because it is a lot of paperwork. If it results in victory sooner for the claimant, however, then it is worth it. This is why I decided to take initial SSD claims. Fortunately this has resulted in a large volume of cases coming my way recently.
The process for taking initial claims is a little different in that you make sure you have the medical records before applying; then you write a medical summary and argument to attach with the filing. The strongest cases often win initially, and they are greatly aided by a persuasively written memo. Experienced lawyers can aid this process--not ones who've only handled a hearing or two.
Because this is such a lucrative area many lawyers who have little or no experience are jumping on the bandwagon. It is important to get the best representation, not just some representation.