Completely disagree. You can DIY speakers, hell even design your own speakers if your knowledgable enough. And you don't need a $50000 rig to measure speakers. Just $100. You don't need to worry about fitment in every shape of ear possible.

It's not hard to design a decent speaker with low distortion. But it's extremely difficult to design a room with good accoustics. That's not up to the speaker designer though, ha! So the IEM designer has to think about your ears accoustical shape, but the speaker designer can ignore your rooms accoustical space.