Or maybe it’s because birds are colorful and lively, can be seen outside just about anyone’s window, are easily photographed, and many actually are easy to identify, even with poor photos.
Whereas liverworts are very small, not colorful, not active, difficult to identify even with good photos, and one generally has to go out and look for them.
p.s.: can you recommend a guide to liverworts (of N. Am.)? It’s likely to make me despair of ever being capable of identifying them (like my lichen and moss books) but I’m always open to appreciating new things…