Some time ago I received an ordinary SMS on the iPad but I couldn't read it until I signed into iMessage! So iMessage app doesn't work like SMS reading app. It

Some time ago I received an ordinary SMS on the iPad but I couldn't read it until I signed into iMessage! So iMessage app doesn't work like SMS reading app. It forces you into using iMessage account to just read an SMS. Later it lures you into using iMessage instead of SMS to make it harder to switch to another OS later.