Photographers are equipment lovers, connoisseurs of mechanical minutiae, aficionados of quality lenses, appreciators of fine design. Some cameras and lenses simply "speak to us": something visceral happens when we hold them and use them.
I personally think this visceral hit occurs more often with older cameras. There is something in the heft and feel of older, mechanical cameras that is missing from many of the newer polycarbonate models. Some of these new cameras are superb instruments, to be sure, and are just what the professional needs, but they don't bring the same aesthetic to the table. Call it "design as art form" or even "form follows function", many older cameras are beautiful machines you can enjoy and savor over and over again. Some are not so beautiful, but have a scruffy personality that makes them endearing. And they still take good pictures. And they're cheap (Leicas being a notable exception). So in addition to being a literal description, "Old Beater" is also a term of affection and endearment. If the term bothers you, you can use the more upscale term "Heritage Camera", but "Old Beater" suits me fine.
So, hats off to the fine cameras of yesteryear! Keep 'em snapping and keep 'em alive! Salut!