I define mental chastity as abstinence at request without the aid of a physical chastity device.
1. it’s free!
2. it is VERY discreet
3. you do not need a physical chastity device, therefore no cleaning, maintenance, lock-in etc
4. it is comfortable, doesn’t restrict you from doing any activity
5. most chastity devices are not 100% secured
6. it goes to a deeper level of submission when one submits his sexuality without the aid of a chastity device
7. it is easier to be teased and denied
8. even when you use a device you must first accept the fact you will not ejaculate without Her permission
9. it makes your willpower as a submissive stronger – important part of obedience training
10. in case of a medical emergency one does not need to quickly remove the chastity
More on this subject in this video that you can watch for free on Youtube.