That was not the case "every time" and I'm not sure it was the case "usually", or in the largest operations. For example, according to Wikipedia, Operation Cast Lead (2008, ~1400 Palestinians dead) started with an Israeli strike:

A six month long ceasefire between Israel and Hamas ended on 4 November, when the IDF made a raid into Deir al-Balah, central Gaza to destroy a tunnel, killing several Hamas militants. Israel said the raid was a preemptive strike and Hamas intended to abduct further Israeli soldiers,[37][38] while Hamas characterized it as a ceasefire violation,[37][39] and responded with rocket fire into Israel.[40][41]

https://en.wikipedia.org/wiki/Gaza_War_(2008%E2%80%932009)

Operation Hot Winter (2010) started with the assassination of a Hamas commander and an incursion into Gaza by IDF:

https://en.wikipedia.org/wiki/March_2010_Israel%E2%80%93Gaza...

Operation Breaking Dawn (2022) started with pre-emptive assassinations of Palestinian Islamic Jihad leaders:

The initial attack included the targeted killing of Tayseer al-Jabari, a military leader of the group.[21][22][23] On the second day, the PIJ commander of the Southern area of the Strip, Khaled Mansour, was also targeted and killed. Islamic Jihad stated that the Israeli bombardments were a 'declaration of war' and responded with retaliatory rocket fire towards Israel.[24]

https://en.wikipedia.org/wiki/2022_Gaza%E2%80%93Israel_clash...

Other "operations" and bouts of violence started without any side clearly breaking a ceasefire, but instead with violence that kept escalating during a period of calm.

The 2021 violence (not a named "operation") e.g. started with violence against, and suppression of the religious rights, of Palestinians in East Jerusalem, and subsequent riots:

https://en.wikipedia.org/wiki/2021_Israel%E2%80%93Palestine_...

The crisis was triggered[34] on 6 May, when Palestinians in East Jerusalem began protesting over an anticipated decision of the Supreme Court of Israel on the eviction of six Palestinian families in the East Jerusalem neighborhood of Sheikh Jarrah.[35] Under international law, the area, effectively annexed by Israel in 1980, is a part of the Israeli-occupied West Bank;[36][37] On 7 May, according to Israel's Channel 12, Palestinians threw stones at Israeli police forces,[38] who then stormed the Al-Aqsa Mosque compound[39] using tear gas, rubber bullets, and stun grenades.[40][39][41] The crisis prompted protests around the world as well as official reactions from world leaders.

But you're right, let's not omit any context. In particular, let's not forget that the Palestinians made several attempts to make progress in the relations with Israel that did not include any rockets whatsoever, after Hamas' election, for example The Great March of Return (2018):

https://en.wikipedia.org/wiki/2018%E2%80%932019_Gaza_border_...

At least 189 Palestinians were killed between 30 March and 31 December 2018.[28]: 6 [29][30] An independent United Nations commission set the number of known militants killed at 29 out of the 189.[5] Other sources claim a higher figure, of at least 40.[31][20][32] Israeli soldiers fired tear gas and live ammunition.[33] According to Robert Mardini, head of Middle East for the International Committee of the Red Cross (ICRC), more than 13,000 Palestinians were wounded as of 19 June 2018. The majority were wounded severely, with some 1,400 struck by three to five bullets.[34]

All of which were crushed with overwhelming force by Israel. And of course, let's not forget what happened when Hamas seemed willing to agree to a long-lasting ceasefire (before the elections): its leaders were assassinated.

According to Tristan Dunning, Israel has never responded to repeated offers by Hamas over subsequent years for a quid pro quo moratorium on attacks against civilians.[176] It has engaged in several tadi'a (periods of calm), and proposed a number of ceasefires.[176] In January 2004, Hamas leader Ahmed Yassin, prior to his assassination, said that the group would end armed resistance against Israel for a 10-year hudna[k] in exchange for a Palestinian state in the West Bank, Gaza Strip, and East Jerusalem, and that restoring Palestinians' "historical rights" (relating to the 1948 Palestinian expulsion and flight) "would be left for future generations". His views were quickly echoed by senior Hamas official Abdel Aziz al-Rantissi, who added that Hamas envisaged a "phased liberation".[178] Israel's response was to assassinate Yassin in March in a targeted Israeli air strike, and then al-Rantisi in a similar air strike in April.[179]

https://en.wikipedia.org/wiki/Hamas#Second_Intifada

Let's include all the relevant information, indeed.