They made it to game 7 of the WS last year and had the best record in the AL this year, so it is kinda understandable.
That's exactly what Seattle (Safeco's) roof is... it's basically a big overhang/umbrella to block rain only (they don't have air conditioning or heat). They'd still get enough wind through the still exposed OF stands.
The fact that Castro made the all-star game proves that the every team gets an all star rule is stupid. That's just second grade stupid.