I suppose the validity could be up for discussion, but there are a great many people who want some amount of coverage from $5,000-$50,000 for 'final expenses.' There are many seniors who wait too long and are either uninsurable or have a health history causing them to be charged premiums that are uncomfortably high. If you are a person who wants to have some cash available at your death, great, convert that preferred best issued policy no matter the health changes in between.
Personally, I am not in favor of expensive funerals, but given some people's inability to put aside money for the future, it can be very helpful to have some cash at the death of a SO, to ease the paying of final bills and making life changes.
Yes, many a physician can set aside their own cash safety net, but then it also depends on one's investment preferences, as you said, a small business is illiquid, so to, can real estate investments be illiquid. Even the stock market can be unattractive to liquidate, for example in fall of 2008 it would not have been an ideal time to require a large chunk of money. Few people are going to put aside 5 figures in a money market to sit there just in case.
No, not everyone needs lifetime insurance (there are plenty of plans now without cash value build up if that is not desired, they are essentially a term guaranteed for life), but some people do need it or want it.
Hopefully many physicians here will be so wise that they have estate tax issues and want coverage for that 😉
I am not disagreeing with most of your premises, it just isn't always cut & dried. I see the checks go out, rarely does the beneficiary feel the insured wasted their money.