If you cross borders your transaction might get stuck. Also some institutions will refuse to send or receive from less popular counterparties. Combine that with all the anti-money laundering regulations and KYC laws everywhere making a bureaucratic mess.
In Swift it's common to specify a routing/intermediary entity which usually is a bigger bank or a branch in NYC/London to work around this mess. And surprise, you get terrible FX rates and magic fees on both ends. One transaction this year across my own accounts took 4 business days and cost ~$40, within the same continent across two top 10 banks. Now I do everything with TransferWise and it's much better. Hopefully soon I'll just use crypto. It's my own hard earned money, damnit. Fingers crossed.