It's mentally taxing to decode amplified speech without the full spectrum of sound, in my experience. Especially with typical cheap devices, and especially when the audio itself isn't all that clear. Tinny, echo-y, scratchy, background noise. In a noisy auditorium, I get a headache pretty quickly with my hearing aids in. People get headaches with hours of phone calls. Common complaint of call centre workers before the pandemic. Zoom fatigue seems to be a similar phenomenon to me. Though you can add jittery lag and poor visual resolution, so the lips are sometimes out of sync with the audio or not distinct, which is also taxing.