It’s also known as parts cleaner, It’s not important but sometimes required for very dirty area of some parts. Most solvents are harmful for plastic parts of fishing reels. But you may use it some metal parts such as shafts, bearings, drive gears, worm gears (except coated parts). I will share some degreasers here I usually use.
It’s very flammable. Never smoke when using Lighter Fluid to degreasing reel parts. Do not use lighter also. I only use this to degreasing for hardened grease on ball bearings of fishing reels. Put all bearings in small glass jar than cover with lighter fluid. After a few minutes, they are pretty much done. Now, leave to dry a few minutes again, than they are ready to re-lube.