In reply to Kryank:
Its not difficult to figure out:
Travel time
Weather
Daylight hours
Indoor bouldering = no need for partner and its casual. Drop in and you'll probably met an acquaintance.
Challenging problems Vs a probable lack of climbs within grade and in condition (during Lockdown I visited several outdoor bouldering spots and most problems are either too easy or too hard, overgrown or surrounded by rubbish (quarries!). I go to two walls which regularly changes c30 problems that give me something to bite into.
Views and the great outdoors - you'll see more walking than climbing! And not freeze your ass off waiting while your partner faffs at a belay etc.
If you don't live close to good quality and extensive outdoor bouldering, the appeal is clear, especially in urban areas are where centres are generally located. They are popular for many reasons.
Post edited at 18:53