Look - is is really too difficult to understand
Plusnet is a low cost brand aimed at the ultra price sensitive.
You can see this by the advertising type -first it was the TV series Big Brother, now it is 'cashback'.
It's hardly aimed at the 'professional qualified in high quality employment' as the socio-economic experts would put it.
Indeed a perusal of the discussion forums would tell you this for yourself.
It is no longer a niche ISP and has not been for many years - it is now a mass market ISP aimed at the 'great unwashed'.
They have not far short of a million subscribers and what an individual subscriber thinks or wants is of no interest to them.
Those who think it is or should be still niche need to move on so something like AAISP, but of course like everything else in life if you want a superb service, phones answered in seconds, high quality tech advise on tap etc then you are going to have to pay for it.