If it's an Exchange DAG, performing a full cut-over may cause a disruption or outage, depending on several factors. (How the DAG is configured, how your DR/ Business continuity testing is configured, etc.)
It's not necessarily that your exchange team is lazy, it may more be a case of it's a giant pain in the nethers to perform.
In my case at [RedactedCo], we have a 4 node DAG (2 nodes in prod, 2 in DR), with a witness server and an alternate witness at our DR site, which is inline with the minimum for the Preferred/Reference architecture. Cutting over is a semi-automatic operation, takes ~15-20 minutes, and is NOT transparent to the business. Failing back or ending the test is about as painful and non-transparent to the business.