Why is .call() necessary when I want to see returned values from a smart contract function? - solidity

Question

In my contract I have this function (solc 0.8.4):
function makeDecision(address person) external returns (string memory name, bool approved) {
require(msg.sender == loanOfficer, "Only the loan officer can initiate a decision.");
require(bytes(applicants[person].name).length != 0, "That person is not in the pool of applicants.");
if (applicants[person].credScore > 650 && applicants[person].credAge > 5) {
applicants[person].approved = true;
}
return (applicants[person].name, applicants[person].approved);
}
When I go into my truffle console and call my function this way loanContract.makeDecision(accounts[1]) everything works fine, but I get a tx receipt as the response.
When I call my function this way via truffle console loanContract.makeDecision.call(accounts[1]) I get the expected response from my function. I am wanting an explanation that tells me why this difference in response occurs so that I understand what is going on on a deeper level. I hate using things without understanding why they work.
If it helps, my contract (which is named LoanDisbursement) was initialized in the console like so: let loanContract = await LoanDisbursement.deployed() and my accounts variable: let accounts = await web3.eth.getAccounts()
any tips would help since I am still learning and diving into this ecosystem. I've not been able to find any decent documentation on this functionality as of yet. Thanks.

Answer 1

Truffle contract functions create a transaction - and return the transaction data.
The call function doesn't create a transaction, it just makes a call. So it cannot return transaction receipt and the authors of Truffle decided to return the function value instead.
Without transaction, the state of your contract is not changed. Which is probably not what you want, and you should always create a transaction when you need to save state changes to the blockchain.
Truffle doesn't return the function value when you're creating a transaction. Using Truffle, there are two approaches that they recommend:
Reading event logs that the transaction produced
Add an event to your function emit MadeDecision(applicants[person].name, applicants[person].approved);, and then access it in your JS code in result.logs.
Calling a getter in a subsequent call.
Tx setValue(5) and then call getValue(). Or in your case:
Tx makeDecision(0x123) and then call applicants[0x123] (assuming applicants is public).