Since its an option and they ask when you renew (well the do for me) I would say they see it as added risk by way of higher payout in the event of a claim. So yes they probably will charge you more if you carry pillion.
Its much prefer to ride without pillion though. Get them to but their own bike
personally I think its a cheek them asking if you carry pillions, do they ask you or these young scrotes in their chavaliers “do you take passengers” no they dont its yet another money making scam from insurers, just like asking how many miles you gonna do, I ride my bike not just look at the thing its blatent discrimination againts bikers…and breathe
Actually they do - insurance companies have started offering lower insurance to young car drivers who do not drive with more than one passenger and who do not carry passengers after dark - all very high risk of accident factors.
Having just renewed my 21 y.o. daughters car insurance (3 years N.C.B.) I could have got decent reductions for low mileage, only 1 passenger at any time, no driving between 9:00 pm and 6:00 am, and a few other bits.
But as she’s at Uni. away from home and beyond parental control, I just settled for the low mileage option and hit the plastic. (Again!)