The Astros want to play Yordan Alvarez in the outfield more to give other players a chance to rest a bit as the designated hitter:

Chas McCormick could be the DH when Houston deploys an Alvarez-Jake Meyers–Kyle Tucker outfield. Espada said Tuesday he expects Jose Abreu to be slotted in at designated hitter on occasion, and I suspect Jose Altuve could get a smattering of DH reps (both to keep his body rested and to get additional at-bats for Mauricio Dubón).

Chron.com

Abreu and Altuve are well into their 30s and McCormick is one of the older youngsters. Alex Bregman players 2024 as a 30 year old, and he could probably use a day off the infield now and then.

The team could also minimize the defensive impact of Alvarez on the field by playing him on days with either high strikeout or high ground ball pitchers on the mound.

In addition, while the sample size is not great, Alvarez in his career hit much better when he is playing in the field.