[ColleenShaver]

The "1/4 practice field" you've probably experienced is what comes with the field from FIRST. Any events that are lucky enough to have more (up to full fields) is typically provided at the generosity of local teams or the regional committee.

However, as was stated by others, lots of venues are very limited in space so even if they were offered more than a 1/4 field, they likely could not accommodate it without a significant cost to team pit space or safe passage ways for the number of people in the venue during regular time or in the case of an emergency.

How teams gain access to the playing field is managed on an event-by-event basis. Personally, up here we choose to have signups for 10-minute slots, which teams can try to trade with other teams if they find they can't make it after they've signed up. We feel this allows teams maximum work time in the pits and fair usage of the practice area.