I disagree a bit here. I used to think that as well, until I tried practically every IEM on the market. ha. None of them are perfect and they all lack something. I personally am going for 100% neutrality. With that said the very few extremely flat IEMs I've tried a lacking a bit of bass. Just a slight boost at the right frequency would make them perfect. EQ isn't always an option on some devices. So if you're using an amp anyway, the right amount of bass boost could be a god send.
If I think "i'll find another headphone that has better bass" it's not going to happen. At least not easily without millions of hours of searching and an endless wallet. Whereas any of the few neutral phones I've found could be rectified with the correct amount of bass at the right frequency range.
So for the "most" part I agree that you should aim for the best possible match of sound preference via your headphones first and foremost. But after that the amp would be the second best help in my opinion to slightly craft the sound to achieve the best results. So I wouldn't call it altering "imperfections" per se, but rather bringing the sound closer to perfect or closer to someone's desire...
That's how I look at it anyway. :-)
I definitely agree, that those small tweaks in regards to bass is always nice to have with an amp, but I think "expecting" that your amp will somehow change the sound signature of your headphones/earphones is unrealistic. Also criticizing a company for not having adjustable bass boost is going about it the wrong way. I love having the option to alter the sound of my headphones through an amp, but I won't expect it to change it dramatically. But I can understand the reasoning behind wanting an adjustable bass boost, it would cater to the needs of everyone, I just don't think it is realistic.