Why would anyone think this is appropriate?!

So I just went to the store and walking there an older guy (abt 55) passed me on his bike.

I'm 26 and pregnant btw.

And while he passed me he said "big boobs", like.. nothing else..

That was so inappropriate, I felt so gross!

I've been self-cautious of having bigger boobs all my life since I was bullied over it in high school as well so I cover them up pretty good too, it's not like I'm showing them all over...

Why would anyone feel like it's appropriate to comment on that anyway?