I guess I just don't understand the obsession with precise tracking of gear mileage.
Are people really swapping brake pads at mile 2872 because that's how long their previous set lasted? Or riding with a squealing chain because it's not scheduled to be lubed for another 87 miles? The gear tracking that Strava provides is an easy way of having ballpark figures on some of your consumables, and that's about it. And that mileage is just a proxy, anyway - your brake pads don't care about mileage, they care about how hard you stop, how frequently you stop, the kinds of conditions that you ride in, etc - and there's always going to be a good deal of variability in those conditions that determine wear more than mileage alone. Besides, most maintenance needs are brought to your attention through other means.
The practical value of precisely tracking equipment mileage is so low that I would be upset if Strava put resources in to that before something of more value like implementing TBT instructions with their (rapidly improving) route planning or figuring out how to bring back reliable app pairing for BT HRMs, PMs, etc.