This is why dermatology involves risk management not just image interpretation. Yes the lesion will likely change with time. Realistically yes, if you have a melanoma that looks like a harmless mole then the diagnosis is likely to be delayed. But remember that these are a tiny proportion of all skin cancers and you are much more likely to get some other form of cancer - most of which occur internally and cannot be seen at all.
This is a good example of what I find frustrating as a patient. Sure, cancers like that may be a tiny proportion of all skin cancers, but if I have it then it's 100% of my skin cancers. And given how serious skin cancer can be, I'd at least want my doctor to let me know how I could get this lesion tested, even if it's out of my own pocket.
The risk of misdiagnosis and thus unnecessary treatment, can mean that such testing can increase your actual chance of dying or decrease your life expectancy. It depends on the case but its why we don't test generically for cancers unless someone is high risk (such as being old)
I agree with you - if a patient is concerned by a specific skin lesion and requests removal then I will support this even it appears harmless particularly if it is new or changing
