Reel-to-Reel tape decks - only meant for headphones?

Admittedly, my exposure to RTR tape decks is limited to consumer models from my dad's collection. What I inherited is mostly various Akai models, with a couple of Sony in the mix, along with some other makers.

I have thoroughly enjoyed tinkering on all the units I inherited, with no lofty expectations on playback sound. My primary goal for each unit has been 'functionality' - anything additional has been gravy. Turns out that a low expectation in playback sound is the best approach with the examples I inherited. If I can get them to playback in a balanced sound, AND record likewise, I consider that a huge win.

SNR is expectedly low with any tape deck, BUT with quality playback gear in the chain, the resulting sound can be quite good. Related to that, I have played around with archiving vinyl onto tape, with impressive results. HOWEVER, the mechanical noise of a tape deck can detract from the overall playback experience in an open listening environment. Let's face it: tape decks are noisy, by nature.

We've all seen vintage photos of tape deck listeners using head-phones. Was that the true intension/use of tape decks?
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