Answering the question you meant to ask, blueray is a physica... just kidding.

LocalSend is basically like bluetooth file sharing over WiFi. Bluetooth, especially the fallback 2.0 is notoriously slow and short ranged. The situation got better with BLE, 5.0 and Long Range. Still, both devices need to speak BT. Ap*le's iOS is well known to ignore BT file sharing capabilities while implementing own proprietary solutions. On desktop, the situation is still bad. I once tried to send a file between two Windows machines via BT, and it was a horrible user experience. LocalSend (and similar) fix this by implementing cross platform apps and using readily available API's to share files with few clicks and reasonably high speed between a plethora of devices. I guess, if you don't have the aforementioned problems, you won't need LocalSend et al.