Interesting. It also seems strange to me that the Paoli/Thorndale Line is the busiest line yet has so few high level platforms.
Any major renovations to a station require high level platforms, and if you read the Capital Budget you'll see that there is a major push to make all of the busy stations on the SEPTA-owned trunk high level. In the interim, the mini high level platforms comply.
The Feds realize there's difference between unfunded mandates and unfundable mandates.
Not only does it have few high level platforms, but many stations are just falling apart. The stairs on the outbound platform of Rosemont are built out of 2x4s haphazardly nailed together, Narberth is standard mid 70s-late 80s terribleness, St. Davids is crumbling, the inbound roof at Villanova has open holes in it and pieces of metal that are falling down... It's like SEPTA (or whoever owns the stations) is just trying to get someone to sue them when they step through a rotten board or get knocked in the head by a falling piece of ceiling.
It really is a shame how so many of these historic buildings have been allowed to rot. Instead of repairing brick platform surfaces, they just slapped down asphalt on them. Instead of rebuilding shelters they get torn down and have a bus stop put up in their place. Luckily it looks like this trend is reversing, though.