What does this lawyer actually do?
Take your money in exchange for a very incomplete representation of your right(s).
Indeed, drafting and filing a claim is only one preliminary stage of litigation, and such claim might not even be in its definite form. Oftentimes a plaintiff amends (whether once or more) the pleadings. This does not have much to do with being pro se litigant instead of represented by counsel, but depends on the course of litigation, discovery, and partial settlements & dismissals.
Can i do it myself?
Yes. Litigation in pro per is permitted in US courts and I typically encourage it, I myself having been a pro se litigant.
However, the pro se litigant needs to undergo a steep learning curve on statutory law, procedural law (aka rules of civil procedure), be able to do legal research, draft & file your pleadings/motions/briefs/etc., take (and/or testify at) depositions, and present your arguments in court hearings.