TL;DR: Having SF2-capable sound cards is not necessary for soundfonts nowadays, but such sound cards can improve responsiveness if your CPU is relatively weak.
EMU10Kx (Live/Audigy) and EMU20Kx (X-Fi except Xtreme Audio) are the last few cards to have hardware synths. However, it seems only the EMU10Kx hardware synths were documented to some extent and supported on platforms other than Windows. I haven't found any more recent sound cards with hardware synths, and the most recent Creative lineups (using Sound Core3D) no longer have hardware synths.
With utilities like Coolsoft VirtualMIDISynth on Windows, and Timidity++ on Linux, having hardware synths is no longer necessary for using SF2 files. It's just that with supported hardware synths, MIDI processing would be handled by the sound card instead of CPU, so you have better system responsiveness and reduced latency, particularly if your CPU is weak.
A few years ago software SF2 synths (like BASSMIDI/VirtualMidiSynth) had very high CPU overhead that there were some apparent hangs/delays during MIDI playback (in some cases MIDI playback would stop completely) in some games, when using large SF2 files while having a relatively weak CPU. I once used such on a laptop with A8-3500M APU and that happened a few times in some games, especially when quickly going back and forth between certain menus that caused background music to change quickly, that the CPU is taking time (sometimes can be as long as ~1s) to process them, and eventually the MIDI playback went haywire (the music stopped working, or sounded completely messed up) that I was forced to restart the game to get music back to normal again.
That kept me from using them intensively at that time, but at present the soft synths have improved and the overall overhead can be considered good enough, as I haven't really observed any significant issues with them recently.