Why spacing is a safety issue, not a style choice
Baluster gaps that are too wide create a risk of a small child slipping through, or getting a head or limb caught trying. This is why spacing is treated as a safety-critical dimension by architects and fabricators, not an aesthetic preference to be maximised for a "more open" look.
General practice
Common practice for residential and most commercial railings keeps gaps narrow enough that a small child cannot pass through — confirm the exact requirement for your specific project type with your architect or applicable local building guidance, since this can vary by use case (a warehouse railing has different requirements than a family home).
How this affects other design choices
Tighter spacing means more balusters per running foot, which affects both material cost and the visual density of the railing. This is one of the trade-offs worth discussing explicitly with your fabricator rather than assuming wider spacing to save cost.
Glass and cable systems
Glass infill (see our comparison guide) sidesteps the gap-spacing question entirely since there are no gaps to worry about — one reason it's popular for family homes with young children.