Sentimental/emotional value has no standing in the world of Immigration Rules.
May I also point out that such cases, of parents coming on visit visas and then overstaying because of "sentimental value" that makes it so difficult for other parents to get a visit visa for perfectly valid reasons.
Broadly, the UK has made it abundantly clear, through the Immigration Rules, that ADRs are not welcome. The SS route will likely be history too in two years time. If there is persistent abuse of visit visas for parents, I would not be surprised if there would be a blanket ban on people over a certain age with any relative in the UK, on the off-chance that they develop an emotional attachment to living in the UK.
If you disagree with the decisions of a democratically elected government, work on getting it changed. Launch a petition (
here is one for you to sign), protest, lobby your MP, vote. But, broadly, the Rules are in agreement with public opinion, as is expected in a democracy.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.