Obviously, people tend to like the look of bikes in their size. Duh. But I don't believe that's what the OP was getting at when this question was posed.

Look at mens' shoes in shoe ads. The art directors who design these ads can choose any size shoe they want – but they all choose the same size: 8D. Why? Because, design-wise, that size shoe has the best proportion of height to length; visually, it makes all men's shoes look better.

It's the same way with bicycles. Visually, smaller bikes tend to have a better proportion of height to length. They "look" right. Large bikes look too tall, ungainly and unbalanced. They appear top-heavy. It's a design thing. If you're not an artist or a designer, you may well think what I'm saying is BS, but if you have a "good eye," you know what I'm talking about. You can like whatever you like, but in terms of design, smaller bikes look better. It's not subjective.