My personal experience with the people I play with is that amount and depth of play stays relatively static across games, but in games where we have mechanical support things feel more tense, stakes are higher, and characters tend to develop in more unexpected ways. In games without mechanical support players tend to engage in lower stakes yet still interesting conversations, push for their goals less, and tend to stick more to preconceived notions of who their characters are.
** innerdude checks his game room for NSA-level surveillance equipment, because clearly
@Campbell has been watching his group **
** accusing stare **
In all seriousness, though, this is 100% the same with my group, especially the bolded bit. Thinking back to the Shaintar campaign in Savage Worlds (where I was a player, not the GM), this observation is surgically on-point. Character advancement in Savage Worlds is focused exclusively on the character's mechanical "schtick". Everything about it is ability/statistics driven; there's nothing in the rules to push/pull/nudge/direct character
motivations.
I'm thinking of one character in particular, played by my best friend, who I've previously described as a talented actor who's done numerous stage productions (and even been paid for it on occasion). I bring this up, because of all the players, he was the one whose character I most expected evolve, because actor creatives are generally very prone to try and dig into
character motivation. It's part and parcel with the skillset.
Yet at no point in 16 months in the campaign did his character evolve beyond his initial conception. At the start of the game, his character was an irascible, impatient-but-kind-hearted brinchie (think: feline humanoid) with paladin-like spell features.
By the end of the game, he was an irascible, impatient-but-kind-hearted brinchie with more powerful spell-like features and wicked-tough unarmed combat skills---but all character development was along an axis of "preconception."
This is who my character is,
I'm going to play to that.
Zero evolution along the character growth axis---
This is what my character wants---how is that going to play out and change how I view my character?