I have a couple of bralettes, and they've actually come in handy in multiple occasions. My favorite are from Free People, but places like Nordstrom and Forever 21 have great alternatives.
If you really like a dress or romper, but it's just a bit too revealing for an everyday occasion, a lacy bralette is a great option to cover up while staying stylish. I love the deep plunging long sleeve rompers, but let's be real - that requires a lot of boob tape or great genetics. If you're not ready to take the plunge (literally) go for a bralette.
I have a backless tank top that is a little bit to tricky to wear without something underneath it. The back of this Free People bralette is so cool and can be worn under so many things!