I think dogs are like people. Some show their feelings more than others.
Carina never gives kisses unless I ask her, but she'll try to be on my lap whenever she can.
With my first Golden, Natasha, I was never sure if she loved me or she wanted to make absolutely sure I loved her. If she went to the backyard even for five minutes, when she came back she wanted me to pet her and make sure that I still loved her.
Since I had Goldens for the last 27 years, and they are love bugs who always followed me like my shadow and were always very happy when I came back home, I just assumed they loved me as much as I loved them.