A bit off the OP topic....well way the heck off the OP topic. The old secondary debate.
A bit more overall perspective is that secondary is an option and a preference. Some like warm beer, some like cold. Some like clear beer, some like cloudy, and some don't see a difference. Some can taste the difference between them, some can't. Some won't even consider drinking a cloudy beer or one with particles and chunks.
In a few cases, secondary has made no difference on the clarity. Some recipes have had great clearing in primary. Most have been messy. Some leave cakes on top, never to drop; interfering with the transfer to bottling bucket. Some end up with buoyant particles/chunks distributed throughout. Waiting even beyond 3 weeks in primary has not helped clear these problem recipes.
Adding finings here can help to varying degrees. Moving to a location for cold crash will help, too. With good siphon control and/or filtering, transferring directly to bottling bucket can be done without particles and chunks in the bottles. Secondary is another technique to help clear and make it easier to have clear beer to the bottling bucket when the recipe produces a messy primary, when clearing methods are not practical, and when siphon technique is less than expert.
Then there are recipes that drop and clear perfectly, leading one to think that they will all be like it. And some brewers are not limited to the # of fermenting vessels or choose to delay the next brew until a primary is empty.
So what is a waste to some, is necessary to others.