Using all-pole filter to model the Room Impulse Response
It's not because of reverberation.

When you want to model the Frequency Response of the room, it's common to simplify your approximation by using either all-pole or all-zero models. You don't want to use the full zero-pole model.

To get some intuition:


zeros correspond to time delays and antiresonances 
poles correspond to resonances of your Room Response


In practice all-zero models are not being used due to various reasons, such as:


required filter length is comparable to the IR length, and almost 40x the length of corresponding all-pole filter
filter will be valid only for specific distances and positions between the source and receiver (remember: time-delays).




That is why the all-pole model is used instead. As mentioned above, poles correspond to the resonances, i.e. standing waves, which are:


independent of the source location (quite intuitive)
independent of the receiver location (except of the nodes)


Additionally the required filter length is way less than in case of all-zero models. According to Mourjopoulos, for $RT_{60}\approx0.5 \mathrm{s}$, the required order is within the range of $50 &lt; N &lt; 500$.  The same author, concludes that all-pole filters are easier to manipulate than all-zero filters, due to their filter length. Morevover, author mentioned that all-pole filters are sufficient approximation than using raw impulse response data.



Here is some literature:


  Mourjopoulos J. - On the Variation and Invertibility of Room Impulse
  Response
  Functions
  
  Mourjopoulos J., Paraskevas M. A. - Pole and Zero Modelling of Room
  Transfer
  Functions