In your opinion why has'nt PBF returned?

In my opinion Maweather left the sport when he had the most to prove . when WW division was about to reach a height where the true P4P king could be crownd. By leaving all he left were question marks . what if margarito vs. mayweather .. cotto vs. mayweather .. paul w. ... quintana...etc. After 10 or 20 years people will be asking Who was the top WW of those times and this argument will come well he was a great fighter but he never faced .... you know what i mean . A true Champion will leave no questions to be answered thats why one of in my opinion the greatest fighters of all time was Sugar Ray Leonard. I think he has'nt returned because he's trying to secure his record as undefeated but thats not how you secure being an alltime great!