As many people have noted, the reasons are primarily historical: 1. BASIC was invented in the 1960s and supported the "teletype" style printing terminals of th

As many people have noted, the reasons are primarily historical: 1. BASIC was invented in the 1960s and supported the "teletype" style printing terminals of that era. Line oriented operation also enabled efficient multiuser/timesharing operation. (BASIC's simplicity, compactness and low resource requirements translated well to early 8- and 16-bit systems.) 2. BASIC traditionally used line numbers as GOTO/GOSUB targets. 3. Bill Gates' original Microsoft BASIC and (Allison et al.'s) Tiny BASIC, which fit in as little as 8KB and 2KB respectively, were the basis or inspiration for many 8-bit BASIC implementations. Both used line numbers for compatibility with Dartmouth BASIC and for line editing on printing terminals and serial CRTs that didn't support cursor positioning. For example, Microsoft/Altair BASIC worked with printing terminals, and Apple (Integer) BASIC for the Apple I worked with a CRT console that (afaik) didn't support cursor positioning. That being said: 1. On systems like the C64 you can move the cursor around on screen, getting a sort of "screen editor" functionality although technically it is still a line editor. 2. As you note, there is no technical reason why labels rather than line numbers couldn't be used, and several 8- and 16-bit BASIC versions supported them; line numbers were optional in implementations such as Digital Research CBASIC or Microsoft QuickBASIC.