Yes, there is. Birders, backyard birders and gear heads.
And don't discount the gear head market. As is true of motorcycles, guns, amateur radio, pocket watches and 4wd vehicles a lot of people spend a lot of money on gear they find interesting in its own right and try to find a "reason" to own it after they buy it. I have a lot of pictures of birds, squirrels, butterflies and other small creatures not because I am a birder but because I enjoy the challenge of getting good images with a really long lens.
It seems like most people on DPReview consider themselves pure artists who consider their gear merely a tool they use use to create beautiful images. If you look at the posts here that is obviously BS. This is a gear forum for gearheads. Photography as an art form and photography as a gear oriented hobby are not mutually exclusive and are both reasons I enjoy photography. But there is nothing wrong with buying gear just because it is interesting.
I will freely admit to doing that. I have bought and sold some old manual focus telephoto lens like Canons FD 300mm f2.8 L with a TC and FD 500mm f4.5 L on Ebay and enjoyed using them. But as a serious photographic tool the lack of IS, autofocus meant they were inferior to much slower modern lenses. And even if they would have had IS their weight would still make a tripod or monopod necessary, The Canon f11 lenses would cost about the same as what I paid for those old lenses on Ebay and be much more useful despite their slower aperture.
These are not intended to be professional lenses. They are aimed at those of us that want a very long lens that is affordable even if it will be useful only in good light or on a tripod for static or slow moving subjects. There is absolutely no way I am going to spend $12,000 on a fast supertelephoto but I would spend $900. Its not like my livelihood depends on my being able to take a picture of a spectacular bird deep in a dark forest. Being able to take pictures of assorted critters in good light would be good enough.
I am looking at switching to FF from m43 now that Olympus has bailed out of making cameras and Panasonic is spending more resources on their FF cameras than m43. But my experience with m43 has shown that a f11 600mm lens is not as completely useless as many here seem to think it is. With m43 the longest telephoto options are a couple of 100-300 f5.6 zooms at f5.6, a 100-400 f6.3 zoom and a 300mm f4 prime. The zooms need to be stopped down a bit if you want really sharp images which makes the f16 equivalent. But in good light they are still very useful. Not suitable for sports. Or wildlife in poor light. And I often use them with a tripod and hope to get a picture when the subject has paused for bit so I can keep the ISO down. But still useful in many situations, inexpensive enough that I can buy them and light enough to travel with.
