Because they aren't financing the albums most of the time. They're just the record label: they get a percentage of sales and a producing fee, but the show itself pays for the album (either as part of the show's capitalization or as a separate raise).
Cast albums are a loss leader and a marketing tool. It's virtually impossible to license a show without one nowadays (which is why some companies like Concord and MTI help to finance cast albums), there are Grammy opportunities, and every show hopes that they are the rare cast album that crosses over (on streaming, on the radio, on TikTok, etc).
It's also possible to produce an album more cheaply nowadays than years ago. Especially if it's a "studio cast recording" or a "concept album," like some of the examples in your link. A Broadway Cast Recording is a whole different thing.
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