Have you tried to encourage your wife to be more "playful" and tease you a bit? or you know that would simply not work?
When my wife and I first got together she was still with her huge Ex and we would juts fool around a bit - at the very beginning we would just kiss and she would give me handjobs. So she knew from the very start that I was much smaller than the Ex but she never said a word - no teasing me at all about my small size. She is quite modest and conservative.
It's only the first time she gave me a blow-job that I started encouraging her to be a bit more playful and tease me. The first time she gave me a BJ -- I will never forget it -- she took my entire fully-erected cock AND my balls in her mouth all at once, without any effort. It was an amazing feeling and I couldn't help but say - "Wow. Where did you learn to do that?" and she just responded without thinking: "I am used to a much bigger cock".
The second she said that she looked at me with panic in her eyes, obviously thinking that I would be very insulted by her comment. But -- to my surprise and hers -- I was immediately turned on by her comment, and just as she started saying "sorry" - I said with a perverse smile: "So Kevin (the huge Ex.) is much bigger than me?". "Well... a bit bigger" she said, not quite knowing how to respond. "Just a bit bigger? I bet he's a lot bigger..."
By then she had obviously realized that I was very turned on by the idea that I was much smaller than the guy she was currently dating and that she was cheating on him with me.
So she started playing along - "He's about twice as big as you are - maybe a bit more". As she said that, I push her head back down on my cock, "forcing" her to keep it all in her mouth, telling her how much I love knowing that I am so much smaller than he is, and then cumming in her mouth. I remember how easily she swallowed all of my cum, and how she kept my entire cock in her mouth long after I had cum and "released" her head.
From that point on - and to this day -- stories about how her Ex (whom she left for me shortly after that first BJ experience) was so much bigger than me has been a central aspect of our sex life...
That's a lot more information than you wanted I am sure... but my point is that my wife was initially not into teasing me, but soon she embraced it.
Perhaps all your wife needs is some encouragement... or maybe not.