There’s a media report that since the Cannes ban on the burkini, sales around the world have increased, especially to non-Muslim women who for many reasons are not comfortable in bikinis.
According to the report, they represent nearly half the market.
For some, it may be a modesty issue (what’s wrong with that?) but for many it offers sun protection & beats lathering on toxic sunscreen. For others, it may be to avoid the body shaming that dominates misogynist society. You may just want to cover up the “wobbly parts” or cellulite or scarring. Nobody wants to be a warrior for women’s rights at the beach; you just want to go there to relax.
Some non-Muslims apparently were concerned it was cultural appropriation but Muslims may see it as imitation being a form of flattery & social integration.