The customer generally doesn't care about your tech stack but "programmer happiness" does factor into the equation.
If there are 2 equivalent stacks that both do the job more or less well but one gives the dev team a good feeling and the other doesn't then that could be a valid reason. Another valid reason is that as a developer or team you learn and grow from trying out new stuff.
But in the end the product and the customer should be leading, of course.
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The customer generally doesn't care about your tech stack but "programmer happiness" does factor into the equation.
If there are 2 equivalent stacks that both do the job more or less well but one gives the dev team a good feeling and the other doesn't then that could be a valid reason. Another valid reason is that as a developer or team you learn and grow from trying out new stuff.
But in the end the product and the customer should be leading, of course.