Well, those may be 2nd-run and bargain theaters. Be nice if they scheduled more IMAX screens again. Those things make bank!
It's way too soon for second run exhibition - that won't be for a few weeks. XI's still in first run, and now that we're out of the first two weeks, the theater exhibitors can make more money on showings. This just proves it's got some legs. Theaters do not add screens for films that are tailing off.
ST possibly added some screens in smaller markets too. Maybe even drive-ins

(Remember those?)
In our area (Indianapolis), even though Night At The Museum II has the IMAX showings now, ST got added midnight IMAX showings Fri-Sat-Sun. It could even add some more IMAX showings depending on how Night At The Museum does in tis IMAX run.