Moreover, if an investment has compound growth you want to leave it untouched for as long as possible. Paying tax more often than you need to interferes with that.
Consider an investment into a fund of €100,000 growing at 5% p.a. for 8 years.
Person C holds the fund for 8 years, then sells.
Value at year 8 = 100,000 x (1.05^8) = 147,746
Tax = 41% x 47,746 = 19,576
Value after tax = 147,746 - 19,576 = 128,170
Net return = 128,170 - 100,000 = 28,170
Person D sells and rebuys the fund at year 4, then sells at year 8.
Value at year 4 = 100,000 x (1.05^4) = 121,551
Tax = 41% x 21,551 = 8,836
Value after tax = 121,551 - 8,836 = 112,715
Value at year 8 = 112,715 x (1.05^4) = 137,006
Tax = 41% x (137,006 - 112,715) = 9,959
Value after tax = 137,006 - 9,959 = 127,046
Net return = 127,046 - 100,000 = 27,046, a difference of €1,123