We can stop freedom of movement
We could always apply limits to the freedom of movement, like in Germany.
Result: Bad
We have the ability to limit the right of residence up to 3 months.
We should also consider how we will now lose this right - making it harder for us to Live, Work, and go on Holiday in the other European countries.
Limits are already implemented in many EU countries (e.g. Germany).
See Article 7 for more information on what rights citizens actually have.
Summary: After 3 months you need to be employed, or have have sufficient resources to not become a burden to the country.
As to why we don't apply these limits - The cost to enforce this is greater than anything we would save, especially because immigrants are net contributors to the UK.
What EU/EEA citizens give: £14.7 billion
What EU/EEA citizens take: £2.6 billion
This is tax and national insurance paid, vs tax credits and child benefits taken (source).
The UK can also "choose, on a case-by-case basis, whether or not to adopt EU rules on immigration, visa and asylum policies" (source).
If you disagree, or would like to add more details, please let me know.
You can suggest a reason for leaving the EU, or look at the other reasons.