There are a bunch of reasons why any staked token can’t be withdrawn before the thawing period, but the most important one is probably this one:
If you allow people to unstake/undelegate without a thawing period, tokens could be allocated multiple times (allocated tokens won’t be able to go to infinity because of the 0.5% delegation tax, but it could theoretically inflate allocated tokens A LOT). This brings a ton of issues, but mainly that you will be able to have more allocated tokens than the total stake tokens, and even more than the total supply, since basically your tokens are still allocated even after you undelegate.
If I recall correctly, that’s the most prominent reason why the thawing period matches up with the maximum lifespan of allocations.
This affects both delegators and indexers, and neither should be allowed to withdraw rewards without a thawing period. Whether 28 days is too much is another topic, and could be addressed by changing the allocation lifespan as well as the thawing period, which comes with other set of issues (mainly for indexers base gas cost).
Having said that, this isn’t a war between indexers and delegators, we are all trying to make the network grow, there’s no reason to pit ones against each other, and I’d like to address a few things that have been said.
Indexers have an extremely expensive base cost, which will only grow with time (especially when queries become a lot more important). Infrastructure and gas costs are the most visible, but you also need a whole team to maintain said infrastructure, and you are also subject to the same opportunity cost as delegators. This doesn’t mean indexers should be handled advantages, but it’s a lot in stake, which makes it needed for them to get a “higher APY”, since that same APY is the one that pays for the bills and the delegators own APY, without indexers, delegators can’t get rewards.
Delegators have a small delegation tax (which seems to be payed off in a few days of rewards, talking from personal experience, since I’m also a delegator), and the obvious opportunity cost, which is present always when investing in any product.
Another thing to take into consideration is that, from my point of view, indexers aren’t requesting privileges to avoid having to go through the thawing period, but rather to be able to unstake and withdraw rewards without having to fully stop their operations to fully unstake everything, because of how token lock contracts currently work.
For people unaware of this, you can only withdraw surplus from those contracts, which means you need to unstake a higher amount than initially deployed, which means that you will need to unstake your whole stake to be able to withdraw rewards, this effectively means you have to stop your indexing for 28 days to be able to withdraw enough GRT to pay for the operation costs.
So, in layman’s terms, indexers are only asking for a way to be able to pay for their associated costs, which is what was initially intended when mainnet launched, without any privileges over delegators.
In that sense, delegators should also be allowed to do the same with their own token lock contracts (basically any token lock contract should allow for rewards to be withdrawn without the need for a full unstake/undelegation), but neither indexers nor delegators should be allowed to bypass thawing periods.
Keep in mind that most indexers have been maintaining infrastructure for about 7 months from their own pockets, and while big operators can afford to do this, small indexers are getting close to a point where they will probably won’t be able to keep up.