I don't understand why simple algo "don't register touches 5mm from the edge" isn't implemented. Or at least give me it in settings. This will allow to use full screen for video etc, but also will be much more convenient. Don't know who iphone handles it, but my current phone (xiaomi) doesn't have it and it's very annoying.

True, but even 4 inches is already a perfectly acceptable display size (and you can push at least to 4.5-4.7 without compromising ergonomics; see the Sony XZ2 compact, the single compact phone in existence in the last 2 years).