This is called market segmentation, and in competitive markets (like, say, flying or hotels) it’s a good thing: it allows the carrier to sell early tickets at very low prices, often well below the actual marginal cost of the last seat, because these losses will be made up by people who have urgent need for travel right now, and so are much less price sensitive. That’s how, for example, RyanAir is able to offer those 20 EUR cross Europe fares, which is well below even just the fuel cost, much less other costs.
How is this a good thing?
And don't tell me it's important for planning loads: The schedules are mostly fixed anyway, and the usage doesn't fluctuate that wildly. In some countries, like the Netherlands, this is not a thing, and the national train (NS) behaves just like a city metro: You wave your pass walking on to the platform, and wave it again on the way out.