Why would you buy a warrant if the stock is over the strike price?

I understand the use case in options because you could place a put on a lower price

Are you suggesting that only out-of-the-money options are useful? And so the only useful options with strikes below the current price are puts? This is incorrect. Calls and puts are traded both in and out of the money.

Volume is typically higher for out-of-the-money options because they help hedge or speculate on extreme moves, but in-the-money options have their uses, such as obtaining leverage with less time decay. (Put-call parity arbitrage also directly connects in-the-money and out-of-the-money option prices.)

In fact, a speculator who buys an out-of-the-money option generally hopes that it will become in-the-money so they can sell it as high as possible -- which would be an odd thing if there were no point in buying in-the-money options!

In-the-money options (and warrants) have both intrinsic value and time value. They are normally not useful to exercise immediately, but this would become so if they trade at or below intrinsic value. So they will generally have a bid close to intrinsic value at a minimum.

Note that warrant pricing differs in detail from option pricing to take into account that warrant exercise involves buying stock from the company itself rather than another trader, but the principles are similar.

A warrant is like a long term option so it's fairly similar to the mechanics of options.

You've posted several examples so I'm going with the one from your comment where RTP is $13, RTP/WS is $3.75 and the strike price is of $11.50

The warrant give you the right to buy RTP for $11.50 which is $1.50 less than it's current price of $13. The $1.50 is called the intrinsic value and the remaining $2.25 cost of the warrant is its time value.

Warrants (and options) have a delta. This is the amount that the warrant will increase or decrease per one point move in the underlying. Loosely speaking, the delta of an ATM warrant is about .50. The further OTM the warrant is, the lower the delta. The deeper ITM it is, the higher it is. So delta is like a participation rate.

Since your warrant is $1.50 ITM, it might have a delta of about .60 (a guess) so that's what you'll make if RTP moves up $1. The higher RTP goes, the higher the delta will go and the more you'll make per dollar up move of RTP.