As much as I love Biyuuden as a whole, Rika & Yui are deffinitally fan service. Yes, they have "Great PVs" but what to you mostly see in the PV? Hm.... boob shots anyone?
"Great songs" Go look what the english translations mean & again, fan service.
Plus all of their concerts/performances are push up bra Rika & Yui bouncing around.
Everyone has their own opinions, the people who think they're fan service are probably right though
I won't argue about fan service being a part of the Viyuden experience, but I think your limiting it to just Rika and Yui is a bit unfair.
H!P and the idol industry as a whole is about fan service.
As much as we love our respective idols, if you put them against actual professional singers like Ayumi, Namie and BoA they would fade pretty quickly.
But fortunately they are as much actors, models and reality stars as they are singers.
Every Alo-Hello and making of PB DVD is pure fan-service. Giving the fans what they want to see.
Backstage at the concert, Furusato segments, Hello!Morning ... all fan service.
It's not just hot pants and cleavage. MoMusu wears them now too and Berryz and C-ute are starting to.