A couple more thoughts...
If you were to build the best speaker you could build within a certain price range, or with certain component's or size limitations, etc., almost every speaker could be improved with some EQ.
If you make the speaker active you can build-in those tweaks in. And once you have an active speaker (with a power supply, circuit board, etc.) it's costs virtually nothing to add some analog "tweaks". I don't think DSP circuitry (plus an ADC & DAC) can be added at an "insignificant" cost, but it is generally less expensive to build the amplifier into the speaker than to have a separate amplifier so the cost is defrayed somewhat. Or if you have a speaker with digital inputs it already has a some kind of "digital processor" and a DAC and it might not be that much more expensive to use a more powerful processor for DSP. DSP can be "more precise" than analog EQ.
Almost all small studio monitors are active and I assume they all have some built-in analog or digital EQ. (I don't know much about "big" studio monitors.) Lots of big concert PA systems also seem to be using active speakers. Home subwoofers are usually active but because of tradition, and for practical reasons, most home speakers are passive. And in most homes it would be "messy" to plug 6 or more surround speakers into power outlets.
If you read Amir's headphone reviews he is almost always able to improve performance with EQ. I haven't read them all but I don't remember any headphone where he didn't recommend some EQ for improved frequency response. Again "tradition" calls-for passive headphones that are interchangeable with different headphone amps. "Theoretically", a headphone could be sold with a specific-matching headphone amp with the necessary EQ built-in. But here, the economics are reversed because it costs almost nothing to build a headphone amp into a receiver, phone, or computer, etc. The matched headphone & amp would be more expensive.