Can i setup Asterisk so everything stays at SIP level?

basically i want to setup an Asterisk server so that I have 2 outside telephone lines (from my own chosen sip provider) that once it is dialed it forwards to an internal “pbx” that has all softphones and strictly IP phones. So basically I should need no extra hardware except the Asterisk server and the IP phones that connect to the asterisk server via RJ45 or whatever, pull an ip and interface with the asterisk server.

Is this possible? cuz I see all this stuff about FXO and all these fancy cards and telephony devices when researching Asterisk and VOIP solutions and I am wondering why everything cannot just be kept IP all the way through

Yes, you most certainly can stay pure IP. We have thousands of channels all IP based. Not a single digium card installed anywhere.

I have often wondered why people still choose non VoIP solutions… anyone here who uses TDM want to share?

A) Reliability (the VOIP is still not perfect not that the PSTN is either)
B) Faxing
C) Carrier’s