As far as I see it, if someone is texting me, sending me emails, ringing my phone line, etc....then they are invading my space, and its up to me whether I respond or not.
It would depend on what mood I was in, and whether I was interested in being bothered to respond or not. And I wouldnt feel that I had to respond to them, just to please them. It might not feel fair to the person sending the message, but I would be more interested in how I felt, and being disturbed, rather than thinking about what their feelings might be.
But I'm not normal, and have aspergers and only 9% empathy,
Dont spend too long dwelling on imaginary reasons why they arnt replying to you. Move on and forget them. They will contact you if they want to.