Parents are not being excluded from governance. Many parents are on the Trust Boards of Academy's and Foundation Schools, as well as Governing Boards in Community, VA and VC schools in positions other than "representative parent". They haven't been elected to their position, they've been co-opted for their skills and abilities.
The difference the White paper will make is that there won't be a requirement for a set number of governors to be elected by the body of parents; the boards will be made up of people who are best able to do the job.
Not all elected Parent Governors are up to the task. They may be popular in the playground with other parents rather than have the skills needed or willingness to learn. Being a school governor requires the commitment of between 5-10 hours a week - readings documents, participating in training/briefings, attending meetings, visiting the school.
In at least one school I know of, an elected parent governor was unable to read or write. In another, Parent Governors were subject to a suspension for breaching safeguarding policies in the school.
Under current legislation, it's not possible for an elected parent governor to be removed from their position, regardless of what they do, or don't do - as long as they turn up to a meeting every few months. That's not fair on the school, because the GBoard is weakened when that place could be taken by a parent with the skills needed, or fair on the other parents, who elected the parent in the first place to do a job.
By removing the requirement for GBoards to include elected parents, the Board is better able to ensure that the right people are around the table. Very often, that person will come from the parent body, all be it that the parent with the skills needed probably wouldn't have been elected by the other parents had there been a vote.
One of the skills all Governors need is a commitment to the school; and the pool of parents is the best place to start looking for that.