multiple buyins

I don't understand the reasons for players not to buy in all at once. I often see players buy in for $100, lose it then throw another $100 on the table. The player is then often frustrated and playing more aggressive. I think this is a poor strategy, it makes more sense to get all ur money into chips at the beginning. I think mentally its just not a good plan, the feeling of losing all ur chips then rebuying has got to throw you off your game. U don't wanna look like a loser at the table but when ur going broke and rebuying in it just looks bad. Not to mention u might play too agressive or out of control if your sitting on the mindset, " ill just rebuy if I lose these"
I see this type of play all the time,
What do u all think?

I do $200 buy ins to keep myself from getting stupid and putting $1000 on the table all at once. :)

I usually buyin at $40 a session which on a cold table can go fast. I will buyin $20 more if the dice are passed to me and i don't have enough chips to carry three bets and odds. My reason it forces me to walk if nothing is going sad to say more often then not i find myself being the lone good shooter at tables. And thisvstrategy is tough when five dollar tables are hard to find