Well, that's because I'm a very, very petty man...
But seriously, it's my opinion that this is a small part of a greater problem - that S'poreans can be quite "yau-kwee". Maybe it's a matter of perspective, and "reasonable" is relative, but by and large, I think even low-ballers know that they are low-balling.
To be fair though, the majority of deals I've made here have been very reasonable and no-fuss.
correction. i think Asians are typically yau-kwee.