Euronext scraps rules on dividend calls
Until a decade ago, it was common for market makers to accumulate massive open interest in call options before dividend. The boosted open interest in in-the-money calls was usually created against related entities under the same holding.
The idea was to take advantage of retail investors neglecting to early exercise their in-the-money calls before dividend. Having a short call non-assigned means pocketing a piece of free dividend. The non-assignments are divided pro rata.