No Avman it isn't.
First and Business class seats are premium products. They cost a lot of money to produce and to operate. If they sell then the flight may operate at a higher profit margin. If they are given away the exercise is usually futile. Many "executive card" passengers have got wise to certain airlines past practices of upgrading "members" travelling on economy tickets to a higher class. In turn those same airlines are questioning the viability of this practice. Why pay for a product if the airline is prepared to give it away.
Staff passengers are only ever upgraded if space is available. It is usually a condition of their employment that they refrain from discussing their discounted or upgraded status with fare paying passengers. They are subject to a dress code. They are subject to disciplinary control from the employing airline. They are not usually "awed" by an environment in which they spend the greater part of their working lives. They also enable the airline to display a full premium cabin to potential future travellers. Upgraded passengers are not subject to any of these constraints and are are more likely to irritate passengers who have paid a premium fare by sharing knowledge of their good fortune.
There are clearly times when it is in an airlines interest to offer certain passengers upgrades ( overbooking, technical problems such as broken seats etc ), but it is not advantageous to give the product to anybody who simply asks for it. If they pay the premium they will most certainly take priority. Simply paying "a fare" does not afford a passenger any priority to otherwise empty premium seats except as otherwise stated. It doesn't matter whose wages those passengers fares contribute to. If the product operates at a loss it contributes nothing and actually places pressure on the whole profit base.
Still I like the concept. The next time I am in waitrose I will try suggesting that I get the same discount the staff get after all I contribute to their wages as well. Hmmm no maybe not !