Probably just marketplace momentum as much as anything. And there are some minuses to actives with DSP that Doodski mentioned in reverse.
An active with amps and built in DSP can make for a great speaker. OTOH, if any part of that goes bad, your whole speaker is bad. Could be a DSP chip gets zapped by voltage spikes, could be an amp let go, or anything. Any one part ruins the whole and people don't like that.
Oh, and XLR's just never took over. I wish they finally would for actives and passives. I don't think it will ever happen however.
Neutrik speaker connectors.... replace all those bananas and bare cable posts.... best thing since sliced bread for speakers... But other than the pro / PA world, it is too late for change in this space.
And yes, XLR's for active speakers - running line level over multiple meters of cable length is not a great idea.
The RCA's are fine for local 50cm to 2m (3m at a pinch) connections, but beyond that, we need something more reliable. (and less prone to interference.
However, market inertia (and cost differential) will mitigate against it, plus the fact that ultimately, the connection to an active speaker won't be analogue at all, but some form of digital streaming... Dante or similar over either WiFi or Wired IP perhaps with POE - either way a single cable to the speaker.... with WiFi a power cable, with Wired a CAT6 cable carrying both signal and power... keeping in mind that POE is currently limited to 30W.
I think that active speakers with RCA connections are a market niche that will almost disappear within 10 years.
Look at all the "smart speakers" around, using bluetooth and WiFi ... they are the future.... right now most of them are distinctly non High-Fidelity - but that is changing.
I think passive speakers will continue, for the same reason that "seperates" continue, but all the other configurations, all the active speaker types, will be going through a huge amount of change over the next decade....
The "speaker" part of it won't change all that much, barring some sort of dramatic technological development in transducers.... but the "Active" part of the equation... and how it connects to everything else - the mainstream speaker of 2035 will be very different from the mainstream speaker of 2005 - and a 2035 speaker may not be able to connect to a 2005 source/pre without some sort of converters.