Well a couple of obvious points which have been made before regarding this.

How are you a premium passenger if you have no status? Flying in CW once in a blue moon does not make you a particularly important customer to BA - sorry if this sounds harsh but it is true. Even a small amount of flying per year would get you bronze which comes with free seat select at T-7 days.

You only have to pay the fee if you want to select before OLCI. If you are happy to wait to OLCI you will pay nothing.

BA are not unique in this policy.

One of the points to all the seat selection fees is that good seats are kept free for selection for those with status - i.e. those that fly BA a lot and spend lots of money with them. Those frequent flyers might be a bit miffed if every time they booked expensive last minute tickets they found the good seats were taken by those booking in sales 10 months out who travel with BA once a year. It is therefore a benefit to those who have status with BA.

EDIT: and as teledude noted the seat selection fees have been around for a few years now (2009?) so presumably you are fully aware of them since yoiu have flown with BA a few times every year?