It boils down to a time and workload management issue. If this info were to be broadcast then it would have to come through visually i.e. uplinked in someway. In the later stages of an approach (<5,000') it really is unwise to have someone off freq getting the latest short final spot winds. If it were to come from ATC, it would need to be a defined format on first contact with tower - which will increase RT workload on the controller. We typically contact tower at about 6-7 miles which is 2000'agl so any info received and final landing flap decision would have to be made in the next 500'. Not impossible but not ideal......
I think this info is best broadcast early (ATIS) and if there is a wind shift above a certain threshold which is likely to have a noticeable affect on the approach in short final that could be broadcast by tower - á la Windshear conditions.
A4