The deposit matching limitations are there for a reason.
If the poker sites
just gave unrestricted 100% first deposit matching bonuses they would go broke. Thousands of people would deposit $100, then cash out their $200. The poker site is out $100.
Even if people planned on playing with their full roll, a lot of people spew money. They'll deposit $100, sit at a table with $1/$2 blinds, then blow it all the first day. They might generate $5 or so in rake. If they got the $100 bonus they'd pay maybe an additional $5 in rake, so the site's out $90.
To keep themselves from hemorrhaging money sites usually make you get enough points that you've paid for your bonus in rake. So to clear $100 you will have paid $100 in rake.
They market it as "100% First Time Deposit Bonus!" because it sounds a lot better than "Temporary Rakeless Play!"