As I've sperged about before (and forgive me if I repeat myself, because this is one of my sperg red buttons), this goes against how the NHS and NICE operate in this country, as they're publicly funded institutions instead of profit driven and therefore have to use evidence based decision making to justify treatments -
consider all lives of all patients whom they serve to be of equal value and, in making decisions about funding treatment for patients, will seek not to discriminate on the grounds of sex, age, sexual orientation, ethnicity, educational level, employment, marital status, religion or disability except where a difference in the treatment options made available to patients is directly
related to a particular patient’s clinical condition or is related to the anticipated benefits to be derived from a proposed form of treatment.
Therefore they don't routinely offer "non core treatments" for trans people like breast implants, FFS, fat sculpting, multiple genital surgeries (e.g. cut balls off now, amhole later), revision surgeries for loss of depth, vocal surgery... because there's no clinical evidence for their efficacy (someone's mental wellbeing isn't demonstrably more functional because they got a rhinoplasty and some lip fillers, they just want it and may be slightly happier with their appearance). Every boob job or hairline revision they cover for a patient is a hip replacement or cataract removal they can't cover, and those show more evidence as having an impact on Quality Adjusted Life Years.
If a young man is dealing with early onset male pattern baldness or a woman is struggling with being flat chested, they might want surgical interventions like a hair transplant or a boob job, but while those procedures might make them feel better about themselves they could also learn to cope with it, and there's lower risk of surgical complications. Even things like lower back pain from massive breasts or mobility issues from knee damage - they'll often push for lifestyle changes and physio over any sort of surgical intervention. And that's without factoring in their staffing issues and massive covid backlog (that's compounding because minor issues have now become chronic conditions).
Harm limitation is a solid rationale. This is why GPs prescribe bridging hormones to trans people who self refer while taking DIY HRT, much like how they prescribe methadone to heroin addicts - safer to have it monitored while waiting for treatment. Likewise IIRC part of the reason GRS got implemented was the risk of self surgery or going to some shady Thai butcher (although mostly because clinical guidelines said it was more effective treatment than trying to therapise away the gender feels).