A city could replace pipes preventatively as part of road resurfacing when the pipes are sufficiently old.

Not that easy. A road resurface, that can be done in a few days worth of work, less if you hire enough machines and staff.

A pipe replacement? Sewer mains at least here in Germany tend to be anywhere from 2 to 8 meters below ground. That's a lot of soil to move. Freshwater mains is below freezing depth, so usually around 1-2 meters below ground. And above that is a ton of other wiring... electricity, phone, fiber, cable tv, gas and district heat/cooling just to name a few, so when you want to replace the sewer mains, it involves a lot of companies, plus the city authorities for coordination, permits, traffic re-routing (a bus route is bad enough - a tram line or a legit full size train line is a nightmare).

Outside of immediate emergency work from a burst pipe, replacement works take years to plan.

	▲	bluGill 4 days ago \| parent [-]
		That it takes years to plan means you have time to work with the road people. We will have to dig this road up anyway don't resurface it. Often they know roads were built sub-modern standard and want to dig it up but it isn't ecconomical. this needs to be done for all roads constantly sometimes the pipes are still good and you resurface, sometimes they will fail in a few years so may as well dig them up since we have to do the road now.