It is a departure from past certification of pilots but there are two
reasons I believe the FAA has allowed this.

#1) Upgrading "Heavy" ultralights. All the ultralight guys were flying
two seaters and calling themselves instructors to get through a
loophole in Part 103. The FAA doesn't want to allow this anymore and
so they have to obtain a SP license and N-number their ultralights
unless it fits into the true Part 103.

#2) Provide access to flying for a new group of people. This was done
by creating the Sport License, which allows you to jump around and try
different aircraft without dropping as much money along the way
(including $300+ for examiner). Aircraft also fall under this, making
it easier to have a Special Light Sport Aircraft licensed, versus a
Standard Certification. You can see this by the 60+ SLSAs flying in
the last three years compared to probably a tenth of that in GA.

The standards for someone to obtain a new SP rating are extremely low
also. For a SP glider it's 10 hours and 20 hours for airplane. I hope
no one does an initial rating in that amount of time, but basically
the FAA wants to make it as simple as possible and get more interest
going in flying. That's good for us!