@steveo4 there's a whole host of reasons.
You could be under cooking basal and topping up with bolus, lots of us do this when basal's need to change before we are aware.
You could be under cooking bolus's for meals.
Your rate of insulin action could have gone down, we have been in various forms of lockdown / reduced activity for some time and lower levels of activity / higher weights can cause insulin needs to increase.
There may be others but perhaps your only just taking time to look at IOB or even work it out and its always been like this.
If your controlling well then I would not worry too much TBH.