The Leica camera's has a classical minimalist design. For Leica form follows function. This is such a contrast to the computerised digital cameras of today.
The bottom line of the Leica camera (film based or filmless) is that it is grounded in the great German tradition of solid engineering. The film based products, like those from Linhof, last forever and do not bring repeat business.
During the 20th century Leica developed excellent technical solutions, supplied reliable goods and created long-lasting relationships with the customers. The main qualities - over-engineering, obsession with detail and an extreme emphasis on durability - demand a price: the products last a lifetime and do not bring repeat business.
The M4-P (1981) was primitive technology compared to the Cannon and Nikon DSLR's that other photographers were using. Leica is a conservative company--the single lens reflex film cameras had eclipsed rangefinders in the 1970s!
The M4-P did not add much to the progress of the rangefinder camera. It is a manual-focus camera and it did not add automatic exposure metering with manual selection of either shutter speed or aperture that was very accurate. I still had to use a hand held light meter or guess the exposure. It was primitive technology compared to the Cannon and Nikon DSLR's that other photographers were using. Leica was a conservative company.
It was the M7 in 2002 that was an important mark in the history of the Leica rangefinder. The M7 had the integration of electronic exposure automation in the classical body shape, and so gave the experienced Leica user a smooth migration path and transition to modern photography as it gave the photographer the ability to react quickly changing light levels.
It increasingly looks to be the case that the days of the continued production in the classical film M-line are numbered, given the decline in film sales in a digital world.