I would imagine staffing would be much more challenging in lower population area. Plus infrastructure could be a concern. I read that the Breaux Bridge and Henderson exits would require major infrastructure upgrades to handle the water requirements
I just mapped it on Google maps. Target on Louisiana Ave is 3 hours and 1 minute to Menge Rd in Pass Christian, MS and 2 hours and 59 minutes to Bucees in Baytown with current traffic. They are going after people traveling long distances - not local commuters or people driving an hour to LC or BR
I-10 at Louisiana Ave is literally right in the middle of both with an adequate exit and infrastructure already in place. It seems like an ideal location based on those factors