vim-startify (GitHub: mhinz / vim-startify, License: Vim) by Marco Hinz adds a startup screen to Vim with a menu that displays recently used files, sessions, and bookmarks. It effectively replaces Bram Moolenaar's message with something potentially productivity enhancing, particularly if you like using sessions.
If, for some reason, you like the idea of customising the startup message, but don't want to use vim-startify, then take a look at
:help 'shortmess'. This is a setting that can be placed in your
.vimrc to customise Vim's behaviour when it starts up. For example, to turn off Bram's message, use
Another option some people like is
A, which turns off the "ATTENTION" message that is displayed when an existing swap file is found.
If you really want to see the message when Vim has already loaded, you can type