Why Is the Bid-Offer Spread Often Wider for Low-Cap Altcoins Compared to Highly Liquid Assets like Bitcoin Futures?

The primary reason is lower market liquidity. Low-cap altcoins have fewer active buyers and sellers, resulting in a shallow order book.

A shallow book means that a large trade can significantly move the price (high price impact), increasing the market maker's risk. Bitcoin futures, being highly liquid and standardized, have deep order books and intense competition, which naturally compresses the spread.