You might want to read the Bitsquare white paper.
BTC-Fiat trades are secured by a combination of measures. This is completely new territory in the crypto world and we want to get it right. Especially since the limit is per trade and not per user. You can do hundreds of 'limited' trades at a time and thereby spread your risk.
The limit protects users since the start of Bitsquare and it is doing so very effectively, as there have been no scam attempts. I wouldn't call it 'a very crude tool'.