Petition Long term multiple entry visitor visa - parents of citizens

Parents of British Citizens of Non-EU origin currently need to apply for visitors visa every time they need to visit their children in the UK, The long term visas are very expensive and are at the discretion of the embassy.

Bring in a new Visa category for parents of British Citizens so the kids can fulfill their duties to their parents and also allow the parents to spend time with their children and grand children.

The visa could have the following rules
1. Only applicable to a parent of a British citizen/passport holder
2. Indefinite visa ( valid until the visa holder dies or the British citizen on whom its dependent on dies)
3. Maximum stay duration of 6 months (like current visitor visas).
4. Reduced duration between visits (minimum 3 months between visits)
4. No recourse to public funds.
5. Not allowed to work in UK.
6. Must pay for medical treatments.

If a British passport holder can bring in his spouse and kids why are his/her parents treated differently ?