First, understand there is no "normal" post processing. You can spend hours on one image and use a dozen tools to achieve what you desire. Or you could convert from RAW to JPEG and call it a day.
If you are already achieving what you desire by simply using Lightroom, that is great. Many of the recent features added to Lightroom have been added to support just that, an all in one post processing environment.
I don't feel like I'm fully taking advantage of the editing capabilities at my disposal.
If you are paying for Photoshop and not using it, of course it is true that you aren't taking advantage of everything. But just because you are paying for it and not using it, it doesn't mean you should just use it needlessly either.
Why you would use Photoshop in addition to Lightroom could be any number of reasons, some which may make sense to someone not familiar with Photoshop and some just out of habit for those of us that have used it for years.
Some of the reasons I personally switch to Photoshop include:
- To use PS only plugins
- To have more control over healing and cloning
- To replace areas of an image (eyes, sky, etc)
- To have more control over fine selections
- To use tools like content aware fill, liquify, etc
- To use layers and full featured masking
Of course the list could be much larger and it all depends on your needs. For the time being, many if not all photographers can benefit from using both tools versus just one over the other.