Bows with all parallels were once much more comman than today. If you like very narrow limbs, less forward taper is desirable. One can keep the back to belly thickness thicker in the recurve section of the limb using parallels. You can increase side taper using less forward taper, often times saving some mass.
Assenhiemer bows used all parallels and they were and are still very highly regarded. I feel depending upon the design either tapers or paralles will work just fine.
I used to use .003 in my recurves but now mostly .0015 or .001 total taper.