B7 has only 2 x 10MHz. It requires at least 2X as many base stations to cover the same area as B3. Running at 2.6GHz, it requires more power than even 2.4GHz ISM WiFi band.Investment wise, it is bad strategy for telcos to use this band.

B7 is technically useless for large countries which needs to deploy wide coverage.
It is only useful for in-building coverage and very highly dense areas such as SG or HK used to offload traffic on B3/B5/B8.

Instead of distributing mixed blocks for each Big 3 telco, its better to award large chunks of blocks for each band to each telco.

Example:
2 x 30MHz for B3 FDD
2 x 35MHz for B5 FDD

1 x 60MHz for B40 TDD

etc.