So how many lens do you need? On the SLR front I have a wide angle zoom, standard zoom and a telephoto zoom.
Then I have a wide prime, a standard prime, a macro prime and a couple of big telephoto’s.
For my Leica its a bit different. Generally a rangefinder is only good with lens from 28mm to 75mm. Leica make a range from about 21mm to 135mm, but for the extremes you either need to use live view, or an EVF if you have a Leica M (type 240).
I currently have lens from 24mm to 50mm for my Leica with the hope to add a 90mm and possibly a 28mm.
Many people choose a lens for its handling or size, I know a photographer who owns and used two different 28mm. A very small f/2.8 version which is his favourite due to its very small size, but also has a f/1.4 for low light use.