Just to expand/clarify this a bit, miners aren't actually performing any 'useful' work while mining, at least not in the traditional sense of the term. They're all just brute force guessing the answer to a puzzle, and when that answer is found it has no use other than satisfying some difficulty threshold used to keep the rate at which answers are found at a roughly constant rate regardless of aggregate miner hashing power. You can run a full node that can be used to validate the integrity of the blockchain without any mining.Instead of trusting a central figure, like you do with traditional currencies, you’re trusting the math behind Bitcoin to ensure everything is on the up-and-up.
Doing all that math requires some computational resources. That’s what your mining rig is--a system that downloads the blockchain, does a bunch of math, and assures the rest of the Bitcoin ecosystem that a given transaction was legitimate.
The code itself changes, Bitcoin core software is still being updated. In some cases, where people don't agree on an update, a hard fork is created. This is how Bitcoin Cash (BCH) came into existence. Supporters believed in increasing block size in attempt to increase transaction throughput, as they felt that not doing so favored treating BTC as an investment (i.e. digital gold) rather than a transactional currency. Many people disagreed with the proposed changes, and that group continued without the changes (Bitcoin), with a new fork with the changes implemented became BCH.Philosophy, or rather "the way it's being used", yes. But the technology (program code) behind it hasn't changed, right?