The difficulty adjustment ensures that, on average, there will always be 6 bitcoins minted every 10 minutes. If the price of the bitcoin increases, miners will be willing to spend more energy to chase those 6 bitcoins. The end result is the network becomes less efficient, as more energy is burned to confirm the same number of transactions.

If difficulty adjustment didn't exist then mining would still be as easy as it was in the satoshi days. The current ASICs would have already finished mining all 21M bitcoins several times over.