Duel markets LSE & TSX5 Jan 2021 22:52
Liquidity
One reason for listing on several exchanges is that it increases a stock's liquidity, which means that there are plenty of shares available for market demand. A dual listing allows investors to choose from several different markets in which to buy or sell shares of the company.
A stock's liquidity can be measured by the bid-ask spread, which is the amount by which the selling price, called the ask price, exceeds the buy price, called the bid price. The increased liquidity for stocks on multiple exchanges makes the stock's bid-ask spread decrease, making it easier for investors to buy and sell the security at any time.
Multinationals
Multinational corporations also tend to list on more than one exchange. These companies may list their shares on both their domestic exchange and the major ones in other countries. For example, the multinational corporation BP (BP)–formerly British Petroleum–trades on the London Stock Exchange, the New York Stock Exchange (NYSE), and several other countries' exchanges.
https://www.investopedia.com/ask/answers/05/stockmultipleexchanges.asp