Sending IR via a wire
Your IR receiver is decoding the high frequency pulsed On-Off-Keying waveform for you. The Arduino doesn't do that.

An IR signal consists of high frequency (say 36KHz) on-off light pulsed at a lower (data) frequency (different combinations to make 1 and 0)



The receiver you have takes that high frequency signal, amplifies it, filters it, and gives you just the resulting 1 and 0 signals. From that the Arduino can use simple time measurements to work out the code.

Without the filtering that the receiver provides the Arduino will have to do all that work by itself - and while that may be technically possible, it's seldom done. You may be able to find a library that can do it, but it's unlikely.