Again, in the narrow context which you describe this, you are correct.
But, there is no reason to NOT have an antenna of resonate length. A
simple motor and a spring loaded real to take up slack will allow you to
construct an antenna of variable length and multi-band capability.
Indeed, only ones knowledge, "macguiverisms", and patience limits one
... as opposed to purchasing a product which is solely, usually, based
on construction costs alone.

I think the post, of mine, which you are responding to, with your above
response, implied all this--I honestly meant to imply such ... or, in
other words, you can only get out what you put in with your efforts,
time, materials, knowledge, techniques, etc.; Or, i.e., the more
thought, design and good construction practices used, the better the
results.

While some of us may search for the most simple constructions, others
will go towards the most elaborate constructions--if anyone is like
myself, complexity grew with understanding, knowledge, patience, etc.

And, as I implied, Roy gave an answer which would have sufficed for,
perhaps, the majority of SWL-ers... I did not fault it (his response),
rather I expanded upon it ... no harm meant here, nor did I intend to
"slight" anyone! HONEST!

Regards,
JS

Actually there is no reason TO have a resonant length antenna if you can
tune it electrically. After all, you may want to tune around some. I can
tell you it is a pain to have to go out and physically make adjustments for
any frequency excursion. There are many nonresonant length antennas that
outperform the resonant length. The 5/8 wave vertical comes to mind. A
long-wire provides a larger capture area. Then there are phased arrays that
reinforce. Look up the HAARP project and see how they made a very large
array and were able to electrically steer the pattern. Cool!

The more you know, the cheaper it gets, and the more you giggle when it
works. The only problem is you get hooked and want to do so much more.