I'm not sure what you heard exactly, but I think there are two possibilities. First, you might have been hearing the adjective conjugations (at sentence endings). You probably know there are four basic sentence endings. For example, for the present tense 가다: 1. 갑니다 (formal-polite) 2. 간다 (formal-plain) 3. 가요 (informal-polite) 4. 가 (informal-plain) But there are adjectives too which are almost like verbs - they conjugate similarly and even have tenses. One of the few differences for adjectives is that the formal-plain (#2) ending becomes the same as the infinitive form. For example, for 크다(big): 1. 큽니다 2. 크다 3. 커요 4. 커, and for 이다(is): 입니다, 이다, 이에요, 이야. So for sentences ending with adjectives(which are common), the formal-plain style will be using the infinitive form. You can think of 집이 좋다, 너 눈이 참 크다, 경기가 나쁘다, 살기가 힘들다, all of which are common phrases. This is one possibility. The other possibility is the class of sentences actually using the verb infinitive form. These are special phrases used for dramatic effect (I'm not sure if there is a name for this). For example, the novel "Gone With The Wind" was translated as 바람과 함께 사라지다. 사라지다 (disappear) is the infinitive form of this verb being used directly without conjugation here. Such forms give a compelling, dramatic feel because it lacks the normal sense of time(tense), as if transcending it. So they are used often for literary titles: 나무들 비탈에 서다. Newspapers may use it for momentous occurrences for effect: 김영삼 역사 속에 잠들다(rests in history). And even in ordinary conversation, people use it to present some concept or event in an interesting or funny way. We seem to see it a lot on TV talk shows and comedies for the same reason. Such phrases may be translated either in present tense (rests) or with an infinitive (to rest). But infinitives are often used in the sense of "is expected to ...", so I think the present tense is preferred. This might be what you have been wondering about.

Since we don't have the supporting verb system we very very rarely use the infinitive form. What you have been hearing is most probably the declarative ~다/~ㅂ니다 conjugation or the proposative ~ㅂ시다 conjugation. https://en.wikipedia.org/wiki/Korean_verbs

You are talking about the basic forms(the dictionary forms, such as 가다, 먹다, 서다) or the present forms(sometimes called as the Plain Style declarative ending in -ㄴ/는다, such as 간다, 먹는다, 선다)?