A330 / why is there one Wing Anti-ice P/B SW and two Eng' Anti-ice P/B SW??

[Juuuune]

I mean why Wing anti-ice P/B is not two?

If Engine anti-ice P/B is one, each engine bleed air(e.g. Trent 700 HPC 3th) can supply own enging lip skin.

I think its has another reason.. about.. engine thrust... or something