The total number of Spike with LOAL and MMPs in service is a tiny fraction of ATGMs. By the way, all the long range (10km+) Spike missiles use RF, not fiber optic.
And yes, you can strap an optical camera onto it but then you would quickly stop dong that when you realised that simple camouflage that even terrorists can use can counter it.
RF has its downsides too, but as I said, these things are always a game of cat and mouse.
Sorry for answering in parts:
1- You said it's rare . Fair point if you compare it with all of the ATGM inventory of all counties. If this paper is correct the number of produced missiles (more than 32000) and production forecast (+15000 missiles after 2018) seems important to me. Also consider future MMP production as it's selected for European BLOS programme.
MBDA is joining with 13 partners and subcontractors from 5 countries to develop a new capability based on the MMP missile system that will be unique for mounted and dismounted forces.
www.mbda-systems.com
2- About missiles with good sensors being expensive vs dumber missiles. TV guidance for munitions is not new. Almost the same sensors would be on RF versions with NLOS man-in-the-loop capability like UMTAS/OMTAS and Spike NLOS variants. So if you think of sensors, combine RF+IIR autonomous+fiber optic missiles together versus all dumb and cheap missiles.
3- A cheap camera or sensor can't detect a vehicle?
Sure, with bad weather it's hard to do... but let me give some examples:
A high speed RC platform with a cheap camera. I think I can detect human sized targets, if unsure you can get closer as a fiber optic datalink will give you realtime 4k+ video easily. If stabilisation becomes a problem, which I think it is not, it can also be solved at the launcher hardware.
What about high speed of the missile causing operator errors?
Speeds perception is relative and perception changes depending on the object distances. See this:
With different lenses you can change it....
4- What about low light conditions, do we need super expensive cameras?
Well maybe for a complete night without a moon, but technology has progressed to a point that a low light cheap camera can perform in twilight better than a human eye.
And nothing stops you from installing a night vision google...
Of course no state will do it. My point is the cost of the missile is getting lower. Maybe Spike is expensive because of R&D costs and because it's a bit rare as you said, so they can charge higher if you need this capability. With radio controlled drones, terrorists or infantry may create problems but it can be stopped with jammers, with fiber optic links it's very hard to stop. Without missiles with sensors (this applies to a subset of RF controlled missiles and fiber optic missiles together), there is no beyond line of sight capability if you want man-in-the-loop, battlefield surveillance, damage assessment and human flexibility in one package.
And the future:
https://www.youtube.com/watch?v=bcZFQ3f26pA