The days where a covered walkway is needed in Southern California are so incredibly few and far between. SNA has a few gates like this too. PLENTY of gates in European and Asian countries with FAR worse weather rely on uncovered airstairs for a large majority of flights. Major airports in Germany, UK, Africa and China all jump to mind from personal experience.

I far prefer it insofar as it's less claustrophobic and far more efficient loading/unloading if they are able to use the front and back stairs.