There are at least a few people who did not have the time or inclination to enjoy a tasty meal in the lounge prior to boarding and at least a few others who happily will have two meals relatively close together.

Knowing you cannot please all the people all of the time, meal service soon after take-off is the easiest way to meet the needs of the largest percentage of people.

Hungry? They are getting your meal out quickly.
Not hungry? Ask them to slow it down.

Delaying my individual meal service is easier than speeding up my individual meal service.