In the early days of DSOs, memory depth was of much greater instant impact on everyday use of a 'scope to look at complex analog signals.
One standard use was to look at one, or several analog video fields, to look at aberrations on the blanking level & sync part of the waveforms.
To this end, to accommodate the around 40ms duration of two fields, the 'scope would be set to around 5ms/div.
Early DSOs often quoted quite decent sample rates, but these were only valid for much faster time/div settings.
At these slow timebase rates, the memory would soon run out of capacity, so as the sweep time was increased, the sample rate was reduced, until a complex wideband video signal became totally unrecognisable.
Over time, memory depth slowly, then rapidly, increased, until that original problem has pretty much disappeared with decent affordable DSOs, & the other niceties of memory depth have become the primary topics of discussion.
There are still DSOs available which are sufficiently low in memory depth that the old problem raises its head. They are usually very cheap, or old.