A PIW in bedok reservoir complain about 2 consec mk 4 on 21 but
not 59 with full scania (on weekends even if not weekdays). Why?
It's simply becos he needs the 21 but for the 'theoretically
perfect" 59 there's no opinions not becos it's full WAB, but
maybe cos he don't rely on it.
Sometimes it's just a matter of which service, timing piw appear
and the available bus at that time. It's sometimes a matter of
chance, say in front of parkway parade a piw who's going Serangoon
North might be infuriated with seeing 2 consec LO3 76. But during
that time, 2 VO3 consec on 196 might get away with it if there's no
PIW along the full trip of the buses. On the other hand, he
wouldn't appreciate it even if u were to say 36 is all WAB since he
doesn't need it!
The moral is like supermarket groceries: U have a risk of stocks
running low and not fulfilling demand, but so long as u don't stock
out when a customer needs them, u're safe. But then, even if u have
abundance of stocks but no demand, they will put to rot in store
also no use. 
Of course there's plenty of WAB services in Bedok Reservoir
& Marine Parade, but what SMB128B talking now is Sengkang
Anchorvale/ Fernvale, where only a pathetic 163 running, where it's
not even WAB, which making it inconvenience for PIW staying around
there. Even when there're more than half of the fleets are KUBs on
163, his mum can't board bcos it's still not PIW accessible.
So should this one and only stock in this supermarket be always
stock up for this case? How would you know it's not in demand?
Of course we are just the minority which can't decide which
services are in demand of WAB, and also not many PIW taking those
WAB either. But if you put yourself in their shoe, you will
understand their frustration. Some PIWs are not rich, but they
still need to travel around, with the simplicity of buses and MRT,
as it cost lesser than taking cabs.
2 cents worth bro.
Cheers.