Traditional wood houses in Scandinavia have tar and seem well preserved: is that usually enough, or did they survive because it’s so cold to six months a year that bugs don’t even try?
Old growth and just 'old' wood is naturally termite resistant because wood gets harder as it ages and the bugs just don't like to chew on it, they will look elsewhere. You don't see many 60+ year old houses getting new termite infestations unless it was in areas of recent repair (fascia boards, brick moldings). But if it's wet, it's softer to chew. It's always comes down to water.
For instance railroad ties were treated with creosote or tar. Similar for the underground part of telephone poles. There was a Copper-Chromium-Arsenic mix also that would kill bugs and mold but is extremely toxic, so isn't EPA approved anymore.
I would not want creosote or tar-treated wood in a house I live in, though. It's all toxic.
In the exterior-treated SPF (think what we use in America for a deck or exterior staircase) there's a durability limit to the rot resistance. And the wood is tough to restore.
Better woods (not necessarily old growth, just white pine or high quality cedar) are easier to restore. They also look nice, so people are more inclined to take care of them.
In the end, nothing lasts forever without maintenance.
Other methods of preventing rot exist such as charring the end of a post before sticking it in the ground, protecting end grain from contact with water, etc.