Email kinda sucks, but at the same time I understand that providers would be doing nothing but fielding phone calls from tirekickers and window shoppers all day if they were to keep their phone as their primary source of contact. Email allows them to get back to them in a more orderly fashion, as well as keep a history of the conversation so they have context and can keep the clients straight.
And, lets face it...email also is a litmus test of sorts to gauge if the client on the other side (or the provider) has at least some rudimentary grasp of the written language. I'm not saying that someone who can't spell or punctuate is an idiot (some of the colleagues I have worked with who are tremendously successful have the written-language skills of an elementary school kid), but it does allow the provider to get some kinda indication of the client.
Three days is a little too late, though. I mean, unless she is very clear in her website or ad that she takes a few days to get back, it's unreasonable to think a client still has any interest 72 hours later.
I PM'd and emailed a new provider on this site, as well as called her. No pickup on the phone, but I received a text later. When I asked her to speak on the phone, she said she only did text until we booked. Well, I don't trust texting because I don't know who the other side is, so that was a dealbreaker.
Two days later, she answers my PM. Three days later, she answers my email.
No thanks.
But I didn't exchange any hostile words with her. I just passed.