Travellers are an exceptional case. What about the people that live their whole lives on those planets, such as your local brokers? Also, perhaps the Traveller lives his whole life until mustering out on just one planet, possibly barbarian? What is considered middle age? In a TL-0 society, this could be 17 or 18. On a TL-15 world, this should be closer to 65 or so. This would also include childhood vaccinations for Travellers depending on the TL of their Homeworld. Childhood vaccinations can vastly alter life expectancy and mostly do not require boosters. That is just one example. I am sure that with thought, we could come up with way more examples as well.
Travellers are indeed exceptional cases. But they are also the only ones rolling on that table. Everyone else has stats and ages according to Referee fiat. Even if the Referee's choice is to use the PC ageing table.
High tech is mostly covered by Anargathics. If a player wants to have ageing table penalties because of the homeworld and background
they chose, I would not stand in their way.
Otherwise, stuff like this can be used to explain emergent dice results, such as why Captain Techno keeps rolling high for ageing, or why Jane the Scout can't seem to do so, probably due that rare dose of Vargr Fever that they caught in term 2.
And... as a point about vaccinations and childhood disease... barring new epidemics, there's a floor to the effect of those on ageing, which the West has pretty much already reached at "almost entirely eliminated". Higher techs can't do much to improve on that - they've moved on to the realm of battling the problems of old age. Otherwise it's more social territory - the areas in the world with the highest child mortality and lowest life expectancy are those in famine or war.
As a 58 year old Australian, I am and I feel middle aged, and have done so since my early 40's. I'm not so sure that's changed for anyone who's avoided major injury or disease in centuries, if not millennia. I know that modern medicine means it's likely I'll have an extended old age, but that's about it. And someone will have to pay for that, either publicly or privately.