Depends on the system. Classical fantasy adventuring? Most if not all sessions. Adventure and Sword&Sorcery? Sometimes, half perhaps. Character drama? Very seldom.
I look at how the system spends its page budget and use that as a guideline. If there is a chapter for combat, one for harm and recovery and one for combat magic then the system wants me to focus on those parts. Also I look at how the players/characters are rewarded and try to have each session hit several of those criteria. So if the only (reliable, non gm-fiat) way to earn rewards if through combat then you bet your sweet ass there will combats each session.
So many. And the answer to all “why nots?”. Time. It’s time. So off the top of my head
Eat the Reich - “The year is 1943. You are a team of crack vampire commandos with one mission: drink all of Hitler’s blood”
Conan 2d20
Legend of the Five rings (5e)
Stoneburner - Deep Rock Galactic the TTRPG
Vaesen - Call of Cthulhu but rooted in nordic mythology
Heart the City Beneath - an award-winning complete tabletop roleplaying game about delving into a nightmare undercity that will give you everything you’ve ever dreamed of – or kill you in the process.