Insert vs Update syntax

When inserting into a table and there are many columns to be inserted
it is hard to synchronize columns to values:

insert into my_table (
    a,
    b,
    c,
    ...many more columns
)values(
    @a,
    @b,
    @c,
    ... the corresponding values
)

Is there some reason for the insert syntax to be the way it is in
instead of the much easier to get it right Update syntax?:

update my_table
set a = @a,
b = @b,
c = @c,
...

Regards, Clodoaldo Pinto Neto