So, lore perspective here:
In the Forgotten Realms (the setting where the eponymous Baldur's Gate is situated and basically one of the 4 continental settings that the world Abeir Toril offers) there are some individuals who even as laypeople devote their lives to a specific deity. Everyone - regardless of if they devoted their lives to a single deity or not - is being claimed at the end of their lives by a specific deity their lives most reflected the virtues of, unless the mortal in question was an atheist, or constantly changed the deity to whom they devoted their lives to.
The vast majority of people in the setting are polytheistic, meaning that they don't devote their lives to a single deity, but rather send prayers to the gods who are in charge of the thing the praying people are trying to invoke or ward off. Most of the people will still have a favourite god based on their profession.
Farmer Marcos for example will likely pray daily - potentially multiple times - to Chauntea, goddess of agriculture and animal husbandry. Whenever one of his farm animals gives birth he'll pray to Lathander, god of mornings, birth and youthfulness, for a save delivery. When his animals fall ill he'll pray to Talona to release his animal from her grip and to Ilmater for a speedy recovery. If he sees a storm comming, he'll pray to Talos to spare his crops and don't push over his home. Farmer Marcos will likely still see himself as being mostly devoted to Chauntea, after all he prayed daily to her and she was the most important deity during the majority of his life.
An optional choice for a favourite god would be welcome for sure, but I'm a bit apprehensive that it would just become the meta to choose a certain deity.
