Spouses can be good cover, which is always useful. On single deck games, it can be useful to have a spouse as a second hand in a rule of six game if you don't want to have to double up your bet on each hand, which is required in many casinos. A spouse playing the table minimum could also be good for hands where it would be useful to eat cards, but you'd have to figure out some signals for that.
If the count is unfavorable, you can let your spouse play your hands for you while you hit the restroom or take a quick break. Casinos are less likely to suspect people of counting when they leave in the middle of the shoe to let someone play for them.