Why doesn't Bitcoin migrate to proof-of-stake? After reading a little bit about different consensus algorithms, I am just trying to understand why Bitcoin still uses proof-of-work. This consensus algorithm being exponentially expensive, and resource intensive, doesn't it make more sense for Bitcoin --the most expensive cryptocurrency out there-- to migrate to proof-of-stake?

Currently, Bitcoin transactions are so expensive that day-to-day transactions, like buying a cup of coffee, can be more expensive than the good/service itself in some parts of the world, which fails to deliver one of the original goals of Bitcoin. That is to be the common person's every-day money.

Why does Bitcoin stick to the proof-of-work consensus algorithm?
Proof of Stake is basically a case of having your cake and eating it, too.
PoW is a simple work-around to a coordination problem that was previously thought to be unsolvable. It sort of &quot;cheats&quot; by providing an economic solution to a distributed systems challenge, by introducing a real cost as a disincentive to unwanted behavior as well as using a reward system both to bootstrap itself and to incentivize security. The advantages of Bitcoin's PoW system include that the group of block authors is truly open to anyone with computational resources, that the system converges on one ground-truth because there is a real cost in producing a competing chaintip, and that it is simple enough for its security model to be well understood.
PoS is more similar to the approaches that were pursued before the publication of Bitcoin. PoS is naturally divergent as there is no real cost in staking. The &quot;Nothing at Stake problem&quot; allows stakers to work on multiple chaintips and only publish the next block from the chain most favorable to them. There are different ways of approaching the vastly different security model of PoS.

Source: Bram Cohen describing ETH's PoS research
For example, ETH's effort to switch to PoS has been in research since at least 2015.
The latest I've read, ETH's current PoS proposal piles multiple layers of complexity on top of the staking to achieve convergence. Stakers have to register as &quot;Validators&quot; of which there are a limited number, put up a sizeable collateral that can be slashed in retaliation for misbehavior, and additionally maintain frozen capital to stake in the first place. More mitigations are in place to punish validator malfunction and recover the system from such breakdowns.
Other approaches to and issues with PoS include:

Some systems introduce a central party that rubberstamps the latest block (e.g. Peercoin). A central coordinating party costs the system its censorship resistance.
It's difficult to fairly launch a PoS system since stakers have to hold funds in the system to author blocks. Many PoS systems get either started as airdrops, Initial Coin Offerings (ICOs), or a proof of burn auction.
Staking requires some representation of the private key to be online at all times, which may mean that it is easier to redirect some of the staking power (in early PoS systems it had to be the actual private key, so not only staking power but actual funds could get stolen). Not participating in staking means that your share in the monetary supply is being inflated away.
Some systems require coins to have a certain amount of confirmations before being allowed to be used for staking, so spending funds interrupts your staking revenue.
Some people expect that staking revenue will be taxed differently than mining revenue.
Some PoS systems can be gamed for profit by trying a vast number of block candidates to cause the staker to get blocks more often than their stake should qualify them for. Such an incentive may turn such PoS systems just into PoW schemes under the hood.
Some researchers argue that &quot;by depending only on resources within the system, proof of stake cannot be used to form a distributed consensus, since it depends on the very history it is trying to form to enforce loss of value&quot;.

So, while the Ethereum Foundation keeps giving (and missing) new delivery dates for an incomplete research project, there seems to be less interest among Bitcoin contributors to discuss Rube Goldberg contraptions.
And then, beyond the general skepsis for PoS, it wouldn't be feasible to just switch to it:

&quot;Even if there somehow was a workable solution that had desirable
properties and security proofs, it would be working under a vastly
different security model than PoW… and nobody can just decide to make
such a change without enormous community consensus for such an
invasive change.&quot;  –Pieter Wuille