- it is explicitly (or at least formerly) not considered a currency
- it is centralized (the company can freeze accounts if it wants, create more coins, or be sued)
- it's major use case is for inter-bank transfers. So if Bank A and Bank B was to exchange currency x for y, they will use XRP in-between. But this gives no value to the currency itself, it is just used as an intermediary. Is it conceivable that Ripple the company will not have enough XRP for these internal bank transfers and they are going to have to buy them back from the public??
So it seems that XRP has no value outside its use by the company Ripple. Is anyone actually using it for commerce or any other reason? It is not considered a store of value like bitcoin (in any case one would want something decentralized.
Generally by looking at the price history, their has been a constant increase over the past weeks in most alternate coins in the market. Last week when the price of bitcoins fell down to ~$13,500, the prices of other altcoins increased by at least a considerable margin. Not to mention, the hype of some people built-up the crowd for a potential pump and dump scheme.
Another reason is that, some investors would ideally diversify their investments into some other coins and not relying into bitcoin alone. With this, they decrease their chances of losing everything and increase the possibility of them earning more in the future.