Exactly. It literally makes no difference if we are or not. So why waste brainpower thinking about it?

It would matter in a number of ways.

For example, we already know thanks to Bell's paradox that local and nonlocal information likely have different governing rules.

If we're in a simulation, then there's also very likely structured rules governing nonlocal information which might be able to be exploited - something we'd have no reason to suspect if not in a simulation.

Much like how an emulated processor can only run operations slowly but there can be things like graphics processing which is passed through from the emulated OS to the host, and that passthrough can be exploited to run processing that couldn't otherwise be run as fast locally, we might extract great value from knowing that we're in a simulation, achieving results that the atomic limits on things like Moore's law are going to soon start to prevent.

Another would be that many virtual worlds have acknowledgements about the nature and purpose of themselves inserted into their world lore.

If we are in a simulation, maybe we should check our own records to see if anything stands out through the benefit of modern hindsight which would indicate what the nature or purpose of the simulation might be.

So while I agree that the personal meaning of life and value it offers is extremely locally dependent and doesn't change much if we are or aren't in a simulation, whether we are could have very profound effects on what is possible for us to accomplish as a civilization and in answering otherwise unanswerable questions about our metaphysics and the nature of our reality.