I'm not young, but I've been using Macintosh computers regularly since 1990, and even back then file names could be up to 31 characters long, and could include any character except colon.¹ So I'm pretty comfortable using spaces, and sometimes even non-ASCII characters, in file names.

Also back then Mac file names typically did not include an extension, because the file's type was stored as part of the metadata in its resource fork. I remember one time a friend of mine was visiting and was playing around with a paint program on my Mac. Being used to DOS, when she went to save her file, she typed a very short name, and then asked me what the proper file extension should be. I smirked and said, "That's not how you name files on a Mac. THIS is how you name files on a Mac." And then I named her file "Ailsa's Cool Picture". Her mind was blown. :-)

¹This is because the colon was the path separator. But since the classic Mac OS had no command line interface, the typical user would never type or even see a file path written out.