For many, small talk does not strengthen or maintain a relationship. It is something that works for some people. Others endure it for the sake of the one who does but it doesn't hold the same role for them and is not a necessity to have a loving and healthy relationship for everyone. Just as we express and receive love differently, small talk doesn't serve the same role in everyone's life. If it does for you, that's great, hopefully you're getting what you need.

As for the double duty, that is true of all communication, whether small or not. As noted above, it may be an expression of love for some people, but it's far from universal.

Not everyone finds the smaller, and often repetitive, experiences of their day to be important or valuable and people are perfectly capable of having time for the other person's life and feelings without the focus being those smaller topics or experiences. Additionally, some people have more important/larger concerns in their day to day life than how the frappuccino from Starbucks was that morning.

It sounds like you value smalltalk in your life but may not accept that it isn't as widespread as you seem to imply. I don't doubt it does what you claim for yourself and others you know. Lastly, what one considers small talk varies greatly, topics of seeming low import may be more meaningful within the shared lives of the couple, depending on what going on.