Why do I find some never called instructions nopl, nopw after ret or jmp in GCC compiled code?

When I compile code with gcc - (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0 - I find in the compiled code some unused code lines at the end of some/all functions or after some absolute jmp.

It seems the result is to align the code, but: Why don't use simply some 0s or NOPs?

The unused code lines I find are something such as the following code lines where I inserted <==:

1. 134d:       eb b7                   jmp    1306 <msb32+0x16>
   134f:       90                      nop    <==
   1350:       b8 ff ff ff ff          mov    $0xffffffff,%eax
   1355:       c3                      retq
   1356:       66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1) <==
   135d:       00 00 00 
   
   0000000000001360 <object_key_compare_serials>:
   1360:       48 8b 07                mov    (%rdi),%rax
   

2. 12fa:       74 44                   je     1340 <msb32+0x50>
   [...]
   1338:       c3                      retq
   1339:       0f 1f 80 00 00 00 00    nopl   0x0(%rax) <==
   1340:       c1 e7 10                shl    $0x10,%edi