1) There's still the opportunity cost of getting it. You're sacrificing almost a whole rifle squad to get it, plus possibly delaying your LT/m20.
2) It can die before you can withdraw it.
3) You only get 75% of the cost refunded.
1) Isn't it better than laying face down in the mud, suppressed?
2) This can be consistently avoided through having more practice of controlling it (hate to say it, but it is l2p issue)
3) The rest 25% is compensated from gaining better map control through using its ability to carry squad and mobility in general