Should you always have a survey done when you buy a house?

Will title insurance cover you if you find out later that there’s an encroachment?

NO, title insurance does not cover encroachments. read the fine print in the title policy.
In Texas, If there is a previous survey available, the owner can sign a avidavit stating there were no changes. If in doubt get a survey done, to protect your investment.
How do you know the fences are in the property line or not? I had a neighbor, who was a cop, who put 2’ of his shed on my lot because it was not fenced.