Probably due to low marketcap of whole crypto industry, it's easy to manipulate such low volume market when you have money (there is also media manipulation).
You may be right but bitcoin has a large capitalization and trading volumes. All the market follows the bitcoin. Perhaps you think that for the entire world market bitcoin has a small trading volume in the cryptocurrency market ?
Bitcoin's volume is unquestionable but specifications of bitcoin cannot be a reason to alternative cryptos. Volumes are mainly created by automated bots that have the ability to pump the real number on our display.