In some places they can (like Colorado) but they don't have the knowledge to know what they're doing a majority of the time. Hell an Intermediate usually doesn't have all the proper knowledge and education needed to know all of why and how they're doing it.
I would certainly agree that most basics in Colorado do not have requite knowledge to start IVs. That said, in many systems there are no Basic/Basic trucks, but almost all P/B, so at least the Basic is starting the IVs under the direction and supervision of a paramedic that hopefully does have the requisite knowledge surrounding IVs.
Also, current CO protocols have provisions for Basics to push front-line cardiac drugs during arrests under the direction of the medic. Presumably this frees up the medic to intubate and work the monitor. Seems to work ok where I am. Realistically I'm not sure how that happens, at least in my area nearly all calls get a P/B ambulance and a fire unit with at least one paramedic.
Just in case your curious to how the protocols read:
SECTION 4 - Medical Acts Allowed for the EMT-Basic
4.6
An EMT-Basic with IV authorization may, under the supervision and authorization of a medical director, administer and monitor medications and classes of medications which exceed those listed in Appendices B and D of these rules for an EMT-Basic with IV authorization under the direct visual supervision of an
EMT-Intermediate or Paramedic when the following conditions have been
established:
a) The patient must be in cardiac arrest or in extremis.
b) Drugs administered must be limited to those authorized by the BME for EMT- Intermediate or Paramedic as stated in Appendices B and D in accordance
with the provisions of Section 3 of these rules.
c) The medical director(s) must amend the appropriate protocols and medical continuous quality improvement program used to supervise the EMS
personnel to reflect this change in patient care. The medical director(s) and
the protocol(s) of the EMT-Basic and the EMT-Intermediate or Paramedic,
must all be in agreement.