It doesn’t “interfere” with anything, they just want you paying attention to the torrent of highly flammable liquid and vapour in your hand.

Some people, like my partner (sorry honey but…) have very poor situational awareness in general, and it plummets to significantly less than nil when they’re on the phone.

I can absolutely imagine someone spraying fuel everywhere, or lighting a cigarette, or some other bullshit because theyre talking on the phone.