Unfortunately, many of the lovely ancient traditions regarding cut flowers have fallen by the wayside and been forgotten. The Romans used cut flowers for sacrifices to the gods and for symbolic purposes during ceremonies and rituals. They were very fond of flower crowns for both men and women for almost every festival and occasion.
There are several different flower languages from different parts of the world of various ages and meanings; the most well-known and remembered in the Western world is that of Victorian England. Most people don't remember it, and there are many online flower language "dictionaries" that disagree with each other as to the various meanings. Idk if yellow roses mean friendship or jealousy, I only know that they're suitable for family members in which you have no romantic interest, such as your aunt or your sister, and girls from Texas love them.
In 20th century American tradition, many women had heirloom vases, handed down through the family or gifted to her as wedding gifts; my mother had two, one handed down and one gifted (one got broken, the other is around here somewhere). These were used on all special occasions and most holidays. If we had a day off work, my mom bought flowers for these two vases, even if they were only cheap grocery store flowers. Trader Joe's has a pretty good selection of cheap but long-lasting flowers and bouquets. Costco used to have a boss selection of cut flowers at reasonable prices, more expensive than Trader Joe's but also bigger bundles and higher quality flowers. Haven't been to Costco in a while so idk.
We know the traditional times to gift flowers---Valentine's Day, Mother's Day, Birthday, and Anniversary. It also used to be traditional at a birth to buy flowers for the mother that represented the sex of the child or plain white, but since women are no longer kept in the hospital after a birth, this has fallen by the wayside. There are also traditional times to BUY flowers--Funerals, Weddings, and sometimes Christmas, but these are not gifts, rhey're straight sacrifices, sometimes masquerading as decor. And of course, flowers are supposed to be part of the courting process--prom corsages and boutonnieres, first date flowers, flowers for the mother of your date or fiancee. These are pretty much gone except for the prom flowers.
The tl;dr absolute reason to buy and gift cut flowers is because it's a cash sacrifice on something frivolous and beautiful that's meant solely for the purpose of the recipient's enjoyment. Therefore, since they're useless and meant only for enjoyment, the cash sacrifice is perceived as more thoughtful and meaningful than it really is. I suggest buying any arrangement that's based around Stargazer lilies (magenta and white) or Casablanca lilies (pure white and very large) due to their very powerful scent, showy looks, and long vase life. Both types of lilies are pretty expensive, the Casablancas moreso than the Stargazers, and the scent of either will stay on your mind for a long while. Both can be grown in the US; idk if they still are. Get one stem of either one of these lilies and have the florist fill it in with various cheap filler flowers like baby's breath, add some cheap greenery, and job done.