The Apple EarPods are a loaded example. They don’t seal to your ear canal at all and have trouble producing bass frequencies as a result. And they’re a $29 dollar product, if we’re talking the wired ones.
And they were still a big step up over the old original ear buds.
Have you ever heard a nicer pair of IEMs with sealing silicone/foam tips? You can get AMAZING sound out of even the tiniest drivers thanks to the magic of acoustic design.
Even the oft-loathed Bose made a really nicely balanced set of IEMs with tiny drivers at one time.
Bose SoundTrue Ultra In-Ear Review - RTINGS.com
The Bose SoundTrue Ultra are above-average in-ear headphones for most use cases. They have a decent sound quality that…
And there are whole communities devoted to buying ever-increasing piles of nice high priced IEMs, and others looking for lower-cost ones that perform well…all of which have drivers that would fit comfortably many times over inside an over-ear pair of headphones.
In-Ear | Headphone Reviews and Discussion - Head-Fi.org
Bluedio T3 Plus (Turbine 3rd) Wireless Bluetooth 4.1 Stereo Headphones with Mic/Micro SD Card Slot (Black)
But hey you can believe what you want to believe. I don’t mind!