I don't think that session IPA's (and low ABV beers in general) need to taste bad, its just harder for breweries to make really good ones. As mentioned a key to a good session is that it doesn't get boring after a few or more. I've had 3 session IPA's that I recall at home on draft. The first one was Firestone Walker Easy Jack which was also mentioned in this thread. It is definitely a good beer but it did become boring about halfway through the keg. I've tried other similar beers which were good on the first beer but your realize that it lacks depth after having it again. Since then I've had two other sessions, Banded Horn Wheat & Potatoes and Deciduous Littles. Both of those beers were still good until the keg kicked. Perhaps the problem as well is for breweries that make big IPA's its hard for them to scale it down. I've had a session IPA from Mystic Brewing in MA which made a really excellent session IPA Echo. In their case their expertise is more in making Saison's so they are used to lower ABV beers. I believe the Echo was also more of a hoppy saison than truly an IPA or at least they used some yeast more typical to Saison's which gave it an interesting twist. They make an incredible Table Beer that is in the low 4% range as well.