Flexibility, flexibility, flexibility. Most manufacturers have a paltry selection of lenses and some of their choices are both puzzling and frustrating, to say the least. The typical 3-9mm lens may be suitable for some applications but in my applications, they typically don't go wide enough to cover a 90+ degree HFOV or narrow enough to cover a table game or gaming machine properly. In other words, the worst of both worlds.
Other issues I've typically encountered, especially with manual lenses we typically prefer are poor fine focus (the focus jumps in discrete steps), adjustments that are too tight (hard to move) or too loose (hard to lock without affecting the setting) and the most vexing - zoom rings that act like focus and focus rings that act like zoom.
For analog cameras, we typically use three lenses: 2.8-12mm (works for maybe 80-85% of applications), 1.8-3.6mm for smaller rooms and area overviews and 5-50mm for longer shots. Wide angle lenses appear to be a rarity for megapixel cameras (except Theia) and the reason for that eludes me. I would think that megapixel offers huge advantages for wide angle shots and wonder why that capability is not utilized often.
In fact, we were so frustrated by the lens options on IndigoVision cameras (Computar 3.1-8mm A-I and Kowa 9-20mm M-I) that we tested our standard definition Computar T4Z2813CS-IR lenses with surprising results: two out of three performed as well as the megapixel lenses with one shortcoming - focus was incredibly difficult to optimize; we often had to get focus as close as possible then utilize the zoom ring to tweak focus.