tl; dr: The easier it is for honest miners to mine compared to an attacker, the more secure is the Bitcoin network.This is a point which seems completely banal to me, but if even Bitcoin's lead developer can be confused about it, it deserves a post.
Don't I care about miners? Really, no, quite frankly. I mean, mining is a zero-sum game, right? So if we make it easier for more miners to start trying to generate bitcoins, that really doesn't do a whole lot for the system.
Mining is indeed a zero-sum game
for miners. The total amount of bitcoins to be gained by mining is fixed by protocol and by the transaction fees users are willing to pay, and if it's easier for one person to mine, what he gains will come at the expense of other miners.
Mining is
not a zero-sum game for
Bitcoin, and this is evident if we recall the main reason mining exists, which is to secure the network. The more people are able to mine, the greater the total honest hashrate, which makes it that much harder for an attacker to overtake the blockchain. Also, more miners means more decentralization, and more difficulty in commiting attacks by compromising specific mining entities.
Note that this isn't a one-to-one "helping X GH/s worth of miners join increases the total hashrate by X". The new miners will increase the difficulty, causing some old miners to leave; a new equilibrium will be reached, which has a higher total hashrate than before.
Following up on the "zero-sum game" theme, doesn't making mining easier also mean it will be easier for an attacker? Well, that depends on how exactly we make mining easier. For example, if some change is done that doubles everyone's hashrate, it will apply equally to honest miners and attackers and thus have no effect.
But any change that gives honest miners an
advantage over attackers, by addressing difficulties that honest miners are more likely to care about, can increase the total honest hashrate without increasing the hashrate that can be amassed by an attacker at a given expense, thus making the network more secure. Some examples of things that can help honest miners (especially at-home miners) more than they help attackers are:
1. Reduce mining variance. An attacker won't have much relative variance, because he is big enough to carry out an effective attack; and he will not care much about the reward or its variance, since the mining reward isn't his main objective.
2. Make mining technically simpler for various use cases. An attacker isn't going to care about technical difficulty; he will hire the best engineers and do it at scale to reduce the amortized cost. For an at-home miner, even a trivial inconvenience can mean the difference between starting to mine or not.
3. Support mining pools. An attacker isn't going to use pools, because he doesn't need them and because he wants control over the blocks. At-home miners must use some form of pool.
4. Make efficient mining hardware available to the masses (or make the hardware available to the masses efficient for mining). An attacker is possibly going to develop his own ASIC solution to be deployed at scale; smaller miners can't afford this luxury, so they should not be left behind in this arms race.
5. Make it possible to leverage existing resources. An ability to mine on the idle CPU of a computer, or a mining device on a PCIe card which can be added to a PC and utilize existing computing, electrical and physical resources will help at-home miners more than an attacker, who will need to make a dedicated purchase of the entire infrastructure.
6. Offer mining assets such as companies and bonds. These will allow people without the means to physically mine to put more funds into honest mining, while being completely useless to attackers. The issuing entity will need some accountability to make sure that it is not itself an attacker.
7. Reduce network latency. The more time it takes to learn about new blocks found, the more hashes wasted on old blocks. Attackers will not suffer from this, because they mostly mine on their own blocks, which they can be instantly aware of.
This also means that some ways to make mining "easier" can arguably actually help attackers more than honest miners, and thus harm network security. Computation/hashing rental services, which give the renter full control of the contents of the computation, if done at scale, can allow an attacker to make a blitz without investing in a long-term deployment.
So if you want the blockchain - the major technical innovation that separates Bitcoin from anything that predated it - to properly do its job of securing Bitcoin transactions, then you should care about mining, you should care about miners, and you should care about changing the Bitcoin ecosystem (which also includes the core protocol) in ways that are beneficial to the typical miner.
