the profit is too little.
You are right. Still, for a non-profession a trader without any technical analysis small profits also matters.
when it comes to smaller altcoins the situation gets worse since they have a bigger spread and nobody trades them.
The big advantage of arbitrage, you can confirm sellers and buyers before you initiate your trades. The chances of getting no bidder is very low as we are not taking big waiting, only confirmation delays usually altcoins have quicker confirmations.
orderbooks are too thin which means you can only buy and sell small amounts sometimes even smaller than the minimum allowed trade size!
When there is no adequate buyers for your volume, you must avoid that trade.