There are many factors that must be held and cannot be sold. For example, playing new shares, because playing new shares requires a certain stock position in the account, so the subscription amount of playing new shares is allocated according to the market value of the shares held. If you sell your shares, you are not qualified to play new shares. There is also a dividend tax issue. The longer the shareholding period, the lower the tax. Then there are margin financing and securities lending, share mortgage loans and so on. These all require a certain stock position.