The newline may also be suppressed by appending `\c' to the end of the
string, as is done by iBCS2 compatible systems. Note that the -n option
as well as the effect of `\c' are implementation-defined in IEEE Std
1003.1-2001 ("POSIX.1") as amended by Cor. 1-2002. For portability, echo
should only be used if the first argument does not start with a hyphen
(`-') and does not contain any backslashes (`\'). If this is not suffi-
cient, printf(1) should be used.
\c Suppress the <newline> that otherwise follows
the final argument in the output. All
characters following the '\c' in the arguments
shall be ignored.
Because if you get in the habit of using printf instead of echo you can avoid having to remember to strip the newline when it matters and only add it when you need it. Though obviously echo is simpler to use for 95% of situations.
¹: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/e...