Winners that weren't on All Stars 7 and why

I've been trying to figure out why some winners weren't on the all-winners season, so I researched and made a list! I wasn't able to find reasons for some of the queens so if you know something I missed please let me know!

BeBe Zahara Bene (S1) - Unknown if she was invited, has stated that the timing was not right for her (that's all I could find)

James Ross [FKA Tyra Sanchez] (S2) - Retired from drag and blacklisted from the series

Sharon Needles (S4) - Blacklisted from the series

Bianca Del Rio (S6) - Was invited back, but declined due to it being of no interest to her along with her busy schedule

Violet Chachki (S7) - no info found

Bob the Drag Queen (S8) - Was not invited to return, but was interested in doing so

Sasha Velour (S9) - I couldn't find anything specific, but she has said in the past that she isn't interested in returning to a competition setting

Aquaria (S10) - I couldn't find anything specific, but when asked if she would do an All Stars season in the past, she stated that she wasn't too interested in the idea

Symone (S13) - no info found

Willow Pill (S14) - Likely won her season too late in regard to when as7 started filming (couldn't find anything concrete)

Chad Michaels (AS1) - no info found

Alaska (AS2) - Was not invited to return, but was interested in doing so

Trixie Mattel (AS3) - Was asked to return, but was too busy to commit to it

Kylie Sonique Love (AS6) - no info found