U.S. dollars from DBS to Interactive Brokers is free ("DBS USA Remit").
The other direction (Interactive Brokers to DBS) is not free. But why do you want to land U.S. dollars at any bank in Singapore?
If you insist you could open a CIMB U.S. dollar current account with US$1,000 to open and no minimum balance thereafter. CIMB hands you a free U.S. dollar cheque book. You could deposit U.S. dollars into that account, and CIMB won't charge anything for the incoming telegraphic transfer. (If there's another bank in the loop that charges a fee is a separate question -- I'm not sure.) Then you could write a paper U.S. dollar cheque and deposit that in another bank. Or just keep the U.S. dollars at CIMB where they'll also be uninsured and also won't earn any interest.
I don't think anybody is suggesting that it is free. Just that according to DBS website, it cost S$10 for inward remittance. but now there is an additional US$10 that JPM charges.
And I don't understand why do you have to keep questioning people why they want to land U.S. Dollar in any bank in Singapore? Did they say it will be in there permanently?
You should know yourself that US$ has many uses and some people may just want to use IB to exchange US$ as the spread is really very good and overall cost might be much cheaper had they just converted with banks. Given that you can directly use IB to pay to other parties easily, is it that difficult to realise that they may have to land it in a bank in Singapore first before transferring it to other parties?
Why the need to be so judgemental and suggest "
if you insist".
List of possible scenarios in case you somehow is not able to figure out yourself
1) Kids studying in the US and needs US$ for daily expenses and school fees
2) Paying bills invoices that are in US$
3) Transferring it to another broker
etc.
Maybe you can share why you didn't think of all these?