Why not, indeed!!

Today we will introduce some of the meanings and usages of the volitional form of a verb and its related expressions.
To make the volitional form of a Group 1 verb (u-verb/strong-inflection verb), replace the last u of the dictionary form with ō: あそぶ(to play) becomes あそぼう. To make that of a Group 2 verb (ru-verb/weak-inflection verb), replace the last ru of the dictionary form with yō: たべる(to eat) becomes たべよう. For the irregular verbs: する(to do) becomes しよう, くる(to come) becomes こよう.
The volitional form is used to express the speaker’s resolution to himself/herself, as in, 明日(あした)からがんばろう (I will do my best from tomorrow). It is also used to invite or make a suggestion to someone who is very close to the speaker in a casual conversation, as Takashi does in Situation 1.
Situation 2: At the office, Mr. Mita is working on a paper.
三田: 明日の会議のアジェンダをアップしようとしているんだけど、何かもうひとつ、忘れていることがあるような気がして…。
グレイ: ああ、LM商事の件ね?あれは、まだ取り上げないことになったよね。
Mita: Ashita no kaigi no ajenda o appu-shiyō to shite-iru-n dakedo, nanika mō hitotsu, wasurete-iru koto ga aru yōna ki ga shite….
Gray: Aa, LM Shōji no ken ne? Are wa, mada toriagenai koto ni natta yo-ne.
Mita: I’m trying to upload the agenda for tomorrow’s meeting, but I feel like I have forgotten one more thing.
Gray: Let me see…, is that about LM Trading? It was decided not to pick it up yet.
The pattern X(verb in volitional form)とする expresses the state that someone is about to do something (X), i.e., X has not started yet, as Mr. Mita uses it in Situation 2, or as in: おふろに入(はい)ろうとしたら、電話(でんわ)がかかってきてしまった。(When I was about to take a bath, there was a telephone call.) Thus, it is usually used for someone’s intentional action, but sometimes as personification, for example: アサガオの花(はな)が今(いま)咲(さ)こうとしている。(The morning glories are about to bloom.)