I *always* keep my phone on silent because I take it with me to business meetings (for actual business purposes; if I need something in the meeting that I don't have, I can text a coworker to bring it to me). So even if I texted someone "can you talk?" I might not see them calling me straight back.
Also, even in Manhattan, cell phone service can suck. There are several parts of my apartment that are absolute crap for phone call signal. I can text from them, I can get texts from them, but if someone called me, it'd go straight to voicemail & not even register as a call on my phone.
My mom (in rural Pennsylvania) has the same problem, except it's less certain parts of the house & more that cell phone service sucks. I've used my boyfriend's phone to call her landline, and then called her cellphone with my cellphone WHILE on the landline with her, to prove that I can be calling her and leaving her a message, and her phone does nothing until after I finish my message. Then it tells her that there's a message. But it supposedly had 4 bars during the whole exchange so...I guess it's a mystery signal.