NASM - Section .data is not working as expected

I am learning about the bootloaders, and I used this code from here https://wiki.osdev.org/Babystep2 to create 'Hello,World!' bootloader.

; boot.asm
   mov ax, 0x07c0
   mov ds, ax
 
   mov si, msg
   cld
ch_loop:lodsb
   or al, al ; zero=end or str
   jz hang   ; get out
   mov ah, 0x0E
   mov bh, 0
   int 0x10
   jmp ch_loop
 
hang:
   jmp hang
 
msg   db 'Hello World', 13, 10, 0
   times 510-($-$$) db 0
   db 0x55
   db 0xAA

The above code works perfectly fine. But when I tried to modify it to use the standard NASM syntax as below, it prints nothing and there are no error messages!

section .data
    msg:    db 'Hello, World!', 13, 10, 0

section .text
    global _start
_start:
    mov ax, 0x07c0
    mov ds, ax
    mov si, msg
    cld
    
_ch_loop:
    lodsb
    or al, al
    jz _hang
    mov ah, 0x0E
    mov bh, 0
    int 0x10
    jmp _ch_loop

_hang:
    jmp _hang
    times 510-($-$$) db 0
    db 0x55
    db 0xAA

The above code doesn't print anything and there is no error message. However when I run the below code it works!

section .text
    global _start
_start:
    msg:    db 'Hello, World!', 13, 10, 0
    mov ax, 0x07c0
    mov ds, ax
    mov si, msg
    cld
    
_ch_loop:
    lodsb
    or al, al
    jz _hang
    mov ah, 0x0E
    mov bh, 0x00
    int 0x10
    jmp _ch_loop

_hang:
    jmp _hang
    times 510-($-$$) db 0
    db 0x55
    db 0xAA

What is going wrong here. Why section .data is not working as expected?