There is only a few reasons of why I won’t reply to an SMS message. One of them is obvious if you understand me, and the other two reasons are pretty obvious, and standard with most people. This page will go into the various reasons of why I won’t answer and SMS message sent to me.
International SMS
The SMS provider does not support international SMS services. Because of this, if someone outside of the US was to send an SMS, I will likely not be able to reply to them. With that in mind, consider sending alternative contact information in your SMS, or use one of the messaging platforms I support. Using a messaging platform will cost in data, so if you are on a limited data service, you would want to keep this in mind.
Scams
I would receive an SMS from my bank telling me of an adverse transaction, and that I must select the link to remedy this issue immediately. I would not reply to such messages. I will not select the link, nor call any telephone number. I will simply just delete the SMS.
Inappropriate SMS
I actually had this happen to me. I received an unsolicited message of how the sender wanted me to fornicate with them in a very particular way. With this in mind, I could have responded rudely, but I chosen to just delete it. And I will delete similar SMS messages that I may receive in the future.