Often because there is no way to get the gas to a power plant. There might not be a local power plant that uses natural gas, or there might not be pipelines, or the local plant might not need the gas.

Methane pops up in many places, and in order to use it for the power grid, you need it to pop up in a convenient place for the power grid.

The only other options left are to flare it, or vent it into the atmosphere. Methane is 40x worse for the environment in its uncombusted form than after burning it, so it's better to burn (flare) it. But sometimes the extractors don't bother. Bitcoin mining provides an incentive for entrepreneurs to seek out methane that isn't being burned, and burn it.

It seems pretty likely that 1) they do and 2) the gas far too much energy to consume onsite. Adding electrified vehicles might help a little.

What I'm surprised is that they cant find a way to add that electricity to the grid, am i right that you must have an internet connection to mine? If so maybe wireless power is the innovation to unlock these distributed sources?

From the article:

“This gas is unable to be sold to a pipeline, so otherwise they’re either venting or flaring the gas. If you are venting the gas you’re just literally venting the methane into the atmosphere,”...

There's probably too much distance between the nearest town or pipeline for the gas to be sold. If not, there's likely some other reason why its not economical for the gas to be used. Otherwise these companies wouldn't be burning away free money. So Bitcoin miners act as a buyer of last resort.

As for it being wasted. What's valuable is purely subjective. That's what makes markets work. Its also why planning economies from the top down doesn't work. What seems like wasted energy or capital to you is very useful to another person. Many people (myself included) believe that a decentralized, digital, hard money that is tied to the real world through energy is extremely important. So to those people its not a waste of energy, far from it.

Or to power some other kind of task. Nobody is posting ads: “hey, need cheap electricity for your industrial thingamajig? See what we can do for you!”