As LEM says, if you forget to arm the speed brakes before landing in the 737-200 and Classic, the lever will come up automatically on selection of the reverse thrust lever (s). While some airlines (again, as LEM has noted) use the reverse thrust levers as the first action in an abort to get the speedbrake lever up, this procedure is contrary to the Boeing recommendation. The speedbrake actuation by use of the reverse thrust lever is in fact the back-up action in event of the pilot forgetting to extend the speedbrake lever on an abort.
The ground and flight spoiler extension is absolutely vital to effective wheel braking and selection of speed brake lever up as the first action after throttle closure (assuming RTO is operating), ensures the weight is on the wheels quickly. On the other hand, with a severe damage engine failure where difficulty may be experienced in getting the reverse thrust levers up straight away, valuable seconds could be lost because the speedbrake lever is still down and RTO is not being able to do the job properly.