Please note that 1 move does not make a position tactical or positional there are very tactical openings in d-pawn openings (lines in the Grunfeld for example) and there are very positional e pawn openings (lines in caro kann for example).
In general hower e-pawn openings do have a tendency to lead to slightly more tactical positons. The reason for this is 3-fold:
1) By opening with you e-pawn you unlock you bishop on f1. That bishop can for example come to c4 attacking the weakest spot in the black camp (f7). Directly forcing black to think about how he will later defend this weak spot
2) Related to reason 1: Opening with the e-pawn also is the quickest route to kingsafety by castling. Once your king is save you can think about opening the center. An open center is generally more tactical then a closed center because it increases the scope of rooks and bishops.
3) The pawn on e4 is itself undefended something that can lead to counterstrikes by black.
d4 generally leads to more quiet positons for the same (opposite reasons)
1) No quick attack on the weak spot f7 and also castling takes longer making it longers that the center opens
2) d4 is defended thus less risk of violet counterstrikes (but not in the grunfeld ! )
3) the logical way to proceed in chess it to first claim as much center as you can (either by pawns of pieces before people begin to whine about the nimzo etc). After d4 it is logical for white to play c4 grabbing more center without creating danger around his king. There is an important difference between c4 and f4 (after e4). In the first case cxd5 is a serious idea (winning the center with tempo on the queen) while in the second case fxe5 leads to trouble due to the white king being a bit drafty (Qh4+). Because white can play d4/c4 the battle is more about how black can stop white from being to strong in the center.
Why are e-pawn openings considered more tactical than d-pawn openings? Also, why are d-pawn openings considered positional? Anything else I should know about them?