[thunfisch]

Low-latency (e.g. less than 20 lines) Videoswitchers/mixers. There's a huge amount of data (12Gbps for 4K/UHD) per input, with many inputs and outputs, all with extremely tight timing tolerances. If you loosen the latency restrictions you can do a small numbers of inputs on regular PCs (see OBS Studio), but at some point a PC architecture will not scale easily anymore and it is much more efficient to just use FPGAs that will do the required logic in hardware. It's such a small market that for most devices an ASIC is not a option.

[mschuster91]

Blackmagic's whole gear line is based on Xilinx FPGAs. Whatever product of them you see, if you tear it down, it will almost always be nothing more than SerDes chips, I/O controllers and FPGAs.