I remember. My point is that the utility argument doesn't really work after 3 or 4 vises for most guys, regardless of the size of the vise, or after maybe twice that for most guys with bigger, non-hobby shops. After 3 or 4, or 7 or 8, it's time to admit that they're just heavy Hummels.
I dunno Lugz, leaving the collecting out of it, there are more types of vises that even your upper numbers. Heck I have 5 different vises in my "special"
category below...
It largely gets determined what your interests are, and the more diversified, the more you will need to work properly even within a catagory there are reasons to need more than one (drill press vises - I have at least 3 DPs needed for what I do...):
I've bolded and in some cases added notation for use of my use cases:
Machinist - Machined Slide - 2 on one bench (one at each and) + one smaller "jewlers" type, maybe on a power arm, maybe on a base you clamp in a larger vise, maybe both... (Think Baby Wilton - and I'm not particularly a Wilton fan but for the smaller ones...) Also may need another larger one with swivel jaws...
Combination - Optional but are very handy (two sets of jaws, nad a Deeper Throat" (depth to slide)...
Pattern - Definitely if you do large odd work
Gunsmith - Definitely for me both bull jaw and parrot jaw
Shop/Garage Inverted "U" channel
Homeowners Exposed screw - I use one for my welding bench as a "ground clamp" for small welding jobs - i use it 90% of the time
Jewelers - See above, but this also include the hand held jewelers vises...
Special - Such as the Zyless portable Multi vise; 3 point rotator pad vise for odd, round parts DP and Milling...; Mini version of the Chinese wonder vise, - makes a great hobby vise for small light work ; Bessy 3 way welding vise for tees and angles; Fly tying vise...
hand vise - Indispensable if you value your fingers for both wire wheeling and grinding
Mini clamp-on - Sometimes the mini Rotator above isn't the right choice as its gt a suction cup base, and I need it anchored...
mini post
drill press - Several sizes both with and without the angle base...
mill vise
Technician's vise - Pana-vise - I have at least 4 distinct types of these, and had used them all.
Woodworkers Vise - at least one...
Blacksmith Post vise - at least one...
Pipe Vise - at least one...
workmate - Minimum 2 the same size needed better if 3 for the bench type, one benchtop, maybe one portable vise/workshop (still looking for the last one)
So I count a minimum of 34, and I don't necessarily have all the "right" vises for the things I'm interested in working on...
Could I live without all the vises I have? Of course; I could sell off maybe half and not miss them at all, but past that I'd be probably start missing the needed utility.