Verizon iPhone 4S has a sim card but the 4 doesn't?

I had a 4S and that had a sim card, but now I have a 4 that broke and I want to put the sim card in the 4S but the 4 doesn't have a card. Why? Why does the 4S have a sim card and the 4 not?

Some iPhone 4 phones have SIM card slots, those were the ones made to use with GSM carriers only (such as AT&T), the iPhone 4 phones that lack SIM card slots are made for CDMA only carriers such as Verizon and Sprint.

The iPhone 4S was made as a dual CDMA/GSM phone, hence why it has a SIM card slot.

Verizon is a CDMA carrier, which doesn't actively use SIM cards. When the 4 debuted it was initially GSM only until February during its time when the CDMA model debuted. The iPhone 4 remained with separate GSM & CDMA models through its active time as the flagship iPhone & still does & will for good (until its discontinued which is expected when the 5S debuts).

When the 4S debuted it was considered a worldphone, both GSM/CDMA in mind & so is the 5.