Frontier Fiber and Verizon Fiber internet are used in my property, Why is ATT fiber not available?

Because they are not allowed to be there per fcc regulations. Att cannot be in frontier territory and frontier cannot be in att territory

I suspect your in either California, Florida or Texas....

In 2015(2016?) Frontier bought Verizon (combined Bell Atlanta, NYNEX (2 baby bells) and GTE) GTE locations for $10.5 billion.  Thus may say Verizon but now owned and ran by Frontier.

If your actually in the NE of USA where Verizon now only operates for hardwired services in 13 states and also have Frontier... then those states are not apart of the 21 states where ATT (SBC, Pac-Tel, Ameritech, Bell South) owns outside plant thus not an option.

It sounds like you're fortunate to even have two other fiber options, when most people don't even have one choice. You must really love AT&T. Yeah it's unlikely you'll see AT&T join that party. Three will be a crowd and that usually doesn't end pretty.