Nice to see a thread revived. I have a bunch of Marantz cassette decks (including an ultra-rare Esotec-branded SD-4000 two-speed. I've only ever found one other mentioned; it was sold in Japan a while back. Non-Esotec SD-4000s are much more common; I keep one around just for comparison.
)
I think there are two questions being considered and answered here: first, why cassettes at all, and second, why not Marantz cassettes? Let's assume one wants to listen to cassettes, and just consider why not Marantz cassette decks?
I think the first reason is that the Marantz decks that match the classic silver-fronted gear (like the 22XX receivers) do not have Dolby C or HX Pro, do not play metal tapes, etc... That is, they pre-date the best tape technology. Therefore, when compared with other later decks like Pioneers CTF-1250, they tend to lose out.
The 2-speed decks, however, make up for it with the faster speed, an inherently superior technology.
It has long been "common knowledge" that the main reason for getting a classic Marantz deck was just to complete a "stack". Just for the looks, really. But I'd bet many of the people who got them for that reason, found themselves playing them sometimes and enjoying it, especially if they have properly fixed up and aligned the decks. They really aren't bad, at all. And they do LOOK gorgeous (or at least I think they do!
) Lit up, they are among the most pretty decks ever built, I think.
Their real drawback is that they don't quite compare well enough with a few of the best other vintage models, and too many people want "only the best". A later 3-head, ultra-stable block deck with Dolby C/HX-pro and perhaps automatic alignment, from TEAC or Nakamichi, WILL SOUND BETTER... but it probalby won't look as pretty, and unless you put them up for a direct comparison, there is no reason not to enjoy the old Marantz deck, especially if it matches and completes a "stack".
Who cares if they "get no love"? That just keeps them cheaper for those of us who like them! [Although I stopped buying them a couple years ago, since I already have all the ones I want.]