Maybe the reason why there aren't much events is because HSR is designed to be a side game

Hoyo is a multi billion company that services multiple games, and they need to make sure each game doesn't get to compete with each other as much as possible.

They often make attempts to move their playerbase from one to another, Genshin and ZZZ(idk about HI3 and Tears of Themis) being main games with quite a lot of content like exploration or battle, mini games, meanwhile maybe Hoyo's intention is to design HSR as a side game so that people can lightly enjoy it without having to spend too much time to clear content. So people who don't have much time can catch up easily while the users with more time to spend can focus on other main games that has much more content to enjoy. Nowadays in the mobile anime gacha game industry, simplifying daily chores, or any 'mandatory content' is very important so that people playing it doesn't feel tired of doing the chores and eventually quitting due to fatigue.

HSR has various systems that simplify content. You just need to clear some domains or play SU just once to get the daily rewards, and when your resin reaches 300, it can still overcap by 1/3 of the original regeneration speed up to 2400 which reduces the importance of logging in frequently. Neither does genshin or ZZZ has such systems. Exploration or the scale of world quests are much more smaller and simple than Genshin too.

I do hope HSR has more various and creative events too because it feels like the devs aren't trying their best at giving players something to play with our characters.