I doubt that many sports shooters will keen on using a lens that's missing 20mm at the long end, at least for professional gigs.
it's a valid argument as well as the weight factor. The next closest thing is the 70-200mm GM, which has a 10% reach advantage, however the weight is about 80% more. You can carry the 28-75 f2.8 + 70-180 f2.8 and it would still weigh less than the GM. Tamron lenses are high on practicality, less on conventional specs.






