Reason #1: If you make the effort to figure it out, it means she’s worth the effort.
You know how you look confident, but on the inside you privately worry whether you measure up? Well, your wife has a different private worry: somewhere deep inside, every day, she wonders whether she is worth loving. Whether she matters. Whether she is lovable.
That question never goes away (just like you probably never get to a point that you feel as confident as you look). So each day, she’s looking for your signals as to the answer to that question. When you say “I love you” it signals that she is lovable. It reassures her that she must be worth loving, when you, this amazing man, make an effort to think through and understand why she might be upset rather than making her simply tell you. For example, it reassures her that she’s special, when you study her enough to know that she is completely frazzled and that it would mean a lot if you offered to take the kids so she can rest – without her having to tell you that.