If you only need 100 Mbps the 3Com 3c905 series of PCI Ethernet cards are still some of the most reliable hardware you can put into your industrial PC that still has PCI slots. ISDN and ax25 are still really useful if you have low-bandwidth but low-latency needs like sensor data.

Now those are niche use cases, but they do exist. However, what’s wrong with removing insecure code for these niche cases? Either someone will step up to actually maintain it, or newer versions of the kernel will be leaner and have less historical cruft.