I didn't say it made it bigger, I said it made it free (which it does unless they stealth nerfed IF and I didn't notice).
For me, it would be putting points in a talent that I would rarely use. I don't cast enough GHs (or FHs or Heals) for SoS to make any real difference to my throughput. Speccing SoS wouldn't really open up any more shield opportunities as it wouldn't be proccing. I find that more frequent penance and big filler heals from atonement more than make up for the lost shields.
Also I'm not only tank healing, I like the ability to flex to raid healing without having to run two pve specs.