Trading bot is very useful if you already know a trading strategy that works. For example like arbitrage, which need to be executed fast and constant monitoring of markets. The arbitrage chance is very few and hard to come by especially within the same exchange, so some will do cross exchanges arbitrage, which is more tedious, because one need to move funds around. In this case bot is certainly needed. A human is not possible to monitor the markets 24/7.

Another better strategy is to trade the perpetual future spread difference across different exchanges, also call "spread trading", where one trade a perpetual futures pair between two exchanges and profit from the convergence and divergence (or widening and narrowing) of the spread. Example: When the spread is widening, one will short on Exchange A and long on Exchange B at the same time. One will then wait until the spread is narrowing and exit the positions by doing the reverse operations, thereby profiting from the spread. You actually don't have directional risk here.

This is a complex strategy, you need to take into consideration for the funding rate as well not to mention you need to calculate the price fast, have very fast fingers ready to click long & short on both exchanges and high concentration at all time. So, having a bot actually help me a lot trading with this strategy.

Cheers.