Different company doing the tracking from your phone, they can monetise it at utilise it in other (nefarious) ways.
Also, a phone is near impossible to get by without. We shouldn't have to accept our phones are tracking us on someone else's behalf, but people have to be a little bit more flexible with those, whereas a "smart-rack" which can track bike journeys is more easily determined to be OTT and can be pushed back against.