Why didn't the White queen take the Black rook here? I was seeing this match on chess.com.

[FEN ""]
[StartPly "18"]

1. e4 e5
2. Nf3 Nc6
3. Bc4 h6
4. O-O d6
5. d3 Bg4
6. c3 a6
7. Nbd2 Nf6
8. Qb3 Qe7
9. Qxb7 Nd8
10. Qb3 Be6
11. Qa4+ Bd7
12. Qc2 g6
13. Nb3 Bg7
14. d4 


The White queen had a chance to take the Black rook, but the White queen came back, why?
I think it's just a blunder from White; the white queen is not at risk of being trapped, nor is it needed for defense. Qxa8 would have definitely been the best move.

Note that the player's ratings aren't that high (no idea how they compare to FIDE ratings though).