Why not?
doing photo retouching you'll want to be importing raw files, sorting and working on them, then exporting to HDD. You're also likely to be backing things up to external HDDs or NAS. I just think an iPad with no USB port and no support for importing raw files is to going to be the primary device for that. And only 128GB on the top end will be used up super quick. I think adobes approach seems sensible in that regard. By all means have the full photoshop tools available to use, but the original files to be worked on will reside elsewhere (NAS/cloud storage is fine for backups but not fast enough for instantly accessing your catalogue)
Now that can be considered a limitation of the hardware, but I think people understand that's how iPad is, so they wouldn't expect major changes. Therefore you would likely consider it a companion device for such work.