Holy balls, how many times have we had this conversation? Will you people ever give it a rest?
And queue yourself not giving it a rest.
First of all, the IAU's definition is for technical and scientific discussions/communications.
Scientific labels tend to be intentionally recognizably distinct from popular ones as lack of distinction is an invitation for ambiguity and confusion.
People would inevitable invent a new set of categories for the eight 'big' planets and the other 'smaller' planets. Some people's new terms would conflict with other people's terms. It would be a mess.
Yes this is what you get for "voting" rather than recognizing more work is needed to build consensus to get everyone save outliers onboard. 1/3 disagreeing isn't a consensus.
On the other hand, if you named the 'big' planets anything other than 'planet', it would lose efficiency. They are the planets that are talked about most often, so it makes sense to give them a short, concise name.
This sounds a bit lame as justifications go... lose efficiency? Since when are scientists in the business of conserving syllables? In astronomy especially they seem to be preoccupied with naming things after _all_ the principals who discovered them.