In my opinion it's a measure for controlling coin privacy. Limits on XMR withrawal will make people prefer to take out their money in a less-private coin.
Compared the other crypto, the trading volume of monero is microscopic. Basically, if Kraken had to go out and put larger orders out on the market moneros market value would explode immediately. The effects would be one of the following:
Kraken has real monero on there balance sheet (no they don't anymore), they would be home safe no matter the price.
or
They have sold their traders, let's say 0.5B USD in monero on the paper, the have basically been short selling. Monero don't shows sign of a dump and this starts to get very risky. If monero pumps ex. to 1000$ Kraken will be in -1.5b USD. Even if the user swapped to BTC and wanted their money out, they would still be insolvent by -1.5b. (I honestly think it is much worse, they have likely sold all their Cryptos in a fractional reserve manner).
Kraken has real monero on there balance sheet (no they don't anymore), they would be home safe no matter the price.
or
They have sold their traders, let's say 0.5B USD in monero on the paper, the have basically been short selling. Monero don't shows sign of a dump and this starts to get very risky. If monero pumps ex. to 1000$ Kraken will be in -1.5b USD. Even if the user swapped to BTC and wanted their money out, they would still be insolvent by -1.5b. (I honestly think it is much worse, they have likely sold all their Cryptos in a fractional reserve manner).
1