I was a little vague, so I thought I would go first.
I like to lap swim, so I usually go through 2 speedo/tyr type suits a year.
We have local hot springs, which I typically visit during the winter. For these you need a bikini because you have to get in and out of the hot pools and alternate with other pools--- you freeze in the winter wearing too much fabric. This is also a relaxing thing--- you want something non-binding, without ruffles or skirts or extra fabric to get pulled on by jets and currents. Also, the water has a high mineral content (incl. iron and sulfur) and can eat suit fabric and discolor suits-- white is a no-go, but even black suits are done after awhile.
Also, we have several local lakes and rivers that are great for boating and other water sports. Some people like to tube or lay out, while other people go river rafting, hiking to waterfall destinations, ski doo, water ski/wakeboard, ect. For me, I like a "sports-bra" like or otherwise practical and supportive two piece. These also tend to get chewed up fairly quickly with our high sediment waters and the amount of sandstone my behind typically comes in contact with.
I haven't been on a beach vacation in almost 6 years, so that isn't a huge deal. My hot springs bikini does occasional double duty if I vacation somewhere with a pool, like when I was in Phoenix a few years ago.
However, in addition to practicality-- I have to think about having to replace 3-4 swimsuits a year, but also consider that I don't live somewhere where I literally "live" in them. So, they aren't good investments for me. Despite being busty, I can't bring myself to spend 60-120 dollars a piece of a bra-size suit only to feed it to our sulfur waters. I also have to think about cute details and extra linings and layered bits retaining lots of water in the winter, or sediment in the summer. Also, the harsh water means that patterns with white and other light colors can turn orange from the iron, but black bleaches. Still-- since everything but indoor lap swimming involves currents, I good fitting decently supportive top is a must.